SRATN Operating Manual

STATIC EXCITATION EQUIPMENT

SRAT N – KENYA

TABLE OF CONTENTS

page

CHAPTER 1 – TECHNICAL PRESENTATION 2

1.1 Generalities 2

1.2 Technical characteristics 2

1.3 Constructive description 4

1.4 Electric circuits description 5

1.5 Operating description 14

CHAPTER 2 – INSTRUCTIONS OF COMMISSIONING 24

2.1 Documentation necessary for setting into operation 24

2.2 Necessary measurement devices 24

2.3 Setting the equipment into operation 24

CHAPTER 3 – REPAIR INSTRUCTIONS. 35

CHAPTER 4 – OPERATING AND MAINTENANCE INSTRUCTIONS 37

S.C. ICPE ACTEL S.A. INSTRUCTIONS FOR OPERATION AND MAINTENANCE

STATIC EXCITATION EQUIPMENT SRAT N KENYA 2 / 37

CHAPTER 1 – TECHNICAL PRESENTATION

1.1 Generalities

These Instructions for Operation and Maintenance refer to the static excitation

equipment for the supply, control and adjustment of the excitation winding for hydro

generators with alternative current exciters (+rotating diodes) that have a rated current

of maximum 25A d.c. and maximum voltage 200V d.c.

1.2 Technical characteristics

1.2.1 Environment conditions

The product is destined to operate in environment conditions corresponding to

the normal climate, climatic zone: N, operating category: 3.

- temperature range: -10...40°C;

- maximum relative humidity: 80% to 30°C;

- environment void of active chemical agents and dust.

1.2.2 Operational characteristics

power supply voltage from internal

power plant services:

3 x 415V a.c. +/-10% , +Null / 50Hz ±5%

power supply voltage from the

transformer linked to the terminals

of the generator:

= rectifier supply voltage:

3 x 90V a.c. - MERILA

3 x 75V a.c. - MARAGUA

supply voltage for fieldflash 110 V d.c. +10%, max. 10A

auxiliary D.C. voltage 110V d.c. ±10%, max.5A

rated current of the rectifier: Max. 20A

maximum output voltage: Minimum 1.2xU rectifier supply

current forcing margin: Minimum 2*In excitation for 20 sec.

voltage forcing margin: Minimum 2*Un

Working modes on MAIN excitation AUTOMATIC and MANUAL

The AUTOMATIC working mode

has the following adjustment and

limitation loops:

- AVR with the correction of Q (cross current

compensation)

- I*sinϕ regulator.

- cosϕ regulator.

- limitation of minimum excitation current

- limitation of maximum excitation current

- inverse time limitation of maximum

excitation current

- limitation of maximum voltage at the



generator terminals

- inverse time limitation of maximum stator

current in the lag

- limitation of running in lead according to P;

- correction of U/f in no load running;

- operating at Q=0 (usually used at the

normal stop of the generator);

The MANUAL working mode (field

current regulator) comprises:

- IEX (exciter excitation current) regulator

- limitation of minimum excitation current

- limitation of maximum excitation current

- limitation of maximum voltage at the

generator terminals

Supply sources: a. Supply from the transformer connected to

the terminals of the generator stator.

b. Supply from internal power plant services

a. Supply from the transformer

connected to the terminals of the

generator stator (field-flash

ignition).

Enables the start-up of the generator without

the presence of the excitation power supply

voltage.

When the speed of the generator is higher

than 90% from nN and there is an excitation

start-up command, the contactor KA shall be

switched on by PLC, the voltage of 110V d.c.

of the battery shall be applied on the field

winding and after the voltage at the generator

terminals reaches 0.5 from UNG (within a

maximum admitted adjustable time from

O.P.), KA shall be automatically switched off

and the excitation on:

- In the MANUAL working mode the

excitation current increase up to Imin exc.

adjustable from O.P.

- In the AUTOMATIC working mode the

excitation current increase up to Istratup

adjustable from O.P.,

Attention!!! - In this working mode the

excitation protections are set into operation

after reaching the voltage of 0.5*UNG (those

related to the presence of the power voltage

in the rectifier).



b. Supply from the internal power

plant services

Enables the operating of the equipment with

the power supply regardless of the on or off

status of the group. The operating mode is

identical to the field flash one, only that KA

is no longer connected on start-up and the

protections are continuously operating.

Field discharging: - at the normal stop or from generator

protections (without faults in excitation) with

inverter followed by discharge on the linear

resistor of the value 2 – 6 times the rotor

resistance by static breaker;

- at faults in excitation by discharge on a

linear resistor of the value 2 – 6 times the

rotor resistance with static breaker.

Working modes on BACKUP

excitation:

MANUAL

The MANUAL working mode (field

current regulator) comprises:

- IEX (exciter excitation current) regulator

Supply sources: Supply from internal power plant services -

Enables the operating of the equipment with

the power supply regardless of the on or off

status of the group.

Field discharging: - by discharge on a linear resistor of the value

2 – 6 times the rotor resistance with static

breaker.

Switching from MAIN to BACKUP

excitation and reverse

With the excitation system and generator

stopped

Cooling down Natural

1.3 Constructive description

The static excitation equipment has the sizes: 700 x 600 x 2200 mm.

It is made as a cabinet with front-back doors.

The protection degree of the cabinet is IP54.

The cabinet is divided into 2 compartments.

The front side of the cabinet comprises:

- PLC of the Allen Bradley type with numeric regulator

- power sources with + 24V d.c. output

- interface relays with PLC, transformers for the adjustment of voltages and currents;

- switch breakers, clip row



- firing pulses boards DCGN (formation and enhancement of impulses) for the MAIN

and BACKUP excitation

- electronic circuit - BASCRN (adaptation block, sensing, conversion for numeric

adjustment) for the MAIN excitation

- analogical regulator (PRGL) for the BACKUP excitation

The rear side of the cabinet comprises:

- excitation transformer;

- field discharge resistors, ballasting resistor, field flash limitation resistor;

- 2 thyristor bridges (MAIN and BACKUP excitation), static breaker for field

discharge, SBR separator (MAIN and BACKUP excitation selection), SAL separator

(supply from the transformer connected to the terminals of the generator stator/ AC

service supply);

- field flash circuit composed of contactor and rectifier diode.

On the cabinet door are assembled the following:

- Allen Bradley operating panel (O.P.) –View panel made up of an alpha-numeric

display device, buttons with figures and functions for the communication with the PLC,

hereinafter called O.P.;

- voltmeter to check the static breakers;

- ammeter and voltmeter for the concerned excitation current and voltage;

- REMOTE/LOCAL CONTROL selection key and potentiometer for the LOCAL set

point control of the BACKUP excitation.

- relay to monitor the temperature of the excitation transformer.

1.4 Description of the electric circuits

1.4.1 Electric power circuit

The power circuit is made of two fully controlled thyristor bridges placed above

the excitation transformer supplied from the internal power plant services. The

protection of the thyristors at over-current is made of high speed fuses. The protection

at overvoltage due to the supply network and the switching of the thyristors is

performed through the individual RC group mounted on the electronic board U9.

The AVR rectifier may be supplied from the transformer connected to the

terminals of the generator stator or from the transformer mounted in the equipment

cabinet, through a cam switch (SAL).

The BACKUP excitation rectifier is supplied from the transformer mounted in

the cabinet of the equipment.

The outputs of the rectifiers are linked to a cam switch (SBR).

The field discharge of the excitation winding is performed by the static breakers

V7, V8 series with field discharge resistor. The static breakers V7, V8 also ensure the

protection to rotor overvoltage higher than 1000V.



The field-flash circuit is made of the KA relay, the VA diode and the limitation

resistance RLA series connected with the field discharge resistor RD.

1.4.2 Adjustment and control circuits

The adjustment and control circuits are divided according to the functional criterion

into:

- supply circuits

- measure circuits

- regulator circuits

- thyristor firing pulses circuits

- protection circuits

- monitoring and parameter setting devices

- SUPPLY CIRCUITS

The supply of the PLC U6 and of the control electronics is performed with the

stabilized voltage of: +24V noted in the scheme B2 (+24V) and B1 (0V).

This voltage is obtained from 220V a.c. - internal services/power supply

(voltage supplies U1, U2) and from the 110V d.c. - battery (voltage supply U3).

Switch mode power supplies U1, U2, U3 are parallel connected, decoupled by

diodes and form the bars B2 (+24V), B1(0V); the pulse transformers supply voltage is

taken from B2 through the diodes V12.1 and V12.2.

- MAIN EXCITATION MEASUREMENT CIRCUITS

In order to obtain the feedback measurements of UG, IG, USIST, Q, P, f, IE, UE,

UEG, the equipment receives from the generator the following signals:

- 3x110V a.c. measure of UG in clips X-8 phase R, X-9 phase S, X-10 phase T.

- 3x110V a.c. measure of Ugrid in clips X-12 phase R, X-13 phase S, X-14 phase T

- 1A a.c. measure of IG in clips X-1 phase R, X-2 phase T, X-4,5 NULL, by supply with

diagram in V.

- measure of the excitation current from the current transformers T6, T7 - 75A/0.15A

mounted on the alternative current circuit of the rectifiers (phase R and phase T) in

diagram V.

- 40V d.c. - MERILA/ 31Vdc - MARAGUA measure of UE from the d.c. power circuit

of the excitation.

The measure circuits from the U5 block (BASCRN) comprise:

The measure circuit UG (voltage at the generator terminals)

- consists of adjustment transformers T1, T3 and rectifying bridges D5, D6;

- the block supplies a feedback signal 3.6V in pin 2, U3 for the generator rated voltage;

- the level of the feedback is established by resistor R26;

The supervision of the feedback voltage is established by means of the circuits U1A,

U1B, U1C and U3. On the voltage decrease on one of the generator phases below



0.2...0.4 from UN (adjustable from D16...D18), the board shall send a signal to PLC by

the saturation of transistor Q34, a signal that shall automatically switch the regulator

from automatic to manual. This will happen only if the excitation current exceeded the

value of 0.5 from the current of no load running (adjustable from R29).

Measure circuit IG (generator stator current);

- consists of: the bridges D10, D11, resistors R39, R40;

- the level of the current feedback may be modified from P2;

- the level of the current feedback is of 2.25V/X3-5 for the generator stator rated

current;

Measure circuit Q (reactive power):

- the formula is used:

Q = Ugen x Igen x sin ϕ

The measure of ϕ is made with D21...D30, U2A, U2C and U3.

Measure circuit P (active power):

- the measure is made of using the formula:

P = Ugen x Igen x cos ϕ

Measure circuit f (voltage frequency at the generator terminals);

- consists of: the bridges D21...D24, integrated circuits U2A, U3

Measure circuit IE (total excitation current)

- consists of: the bridges D8, D9, resistors R33, R34

- the level of the feedback may be modified from the potentiometer P1;

- the level of the excitation current feedback is of -2.25V/X3-3 for the rated excitation

current;

All measure circuits, i.e. Ugen, Iex, Istator, f, ϕ are transmitted to PLC in numeric

form through the processor U3.

This processor has inscribed a program that reads the converter AN0 (Ugenerator),

converter AN1 (Iex), converter AN3 (Istator or Ugrid), computes f according to the

impulses from RB0 or ϕ according to the impulses from RB0 and RB4.

The read or computed measures are transmitted according to the requests of the

PLC, as follows: on the first 2 bits the transmitted measure, on the following bits is set

1 to transmit the first 5 bits of the measure to be transmitted (the most significant ones)

or 0 to transmit the last 5 bits of the measure to be transmitted.

Remark: for ϕ , the first two most significant bits represent the sign, i.e. 11 for

lag, 00 for lead.

The changing of the significant bits with the transmission of less significant bits

is performed automatically at 0.5 ms from the transmission of the significant bits.

All input measures are sampled on 10 bits (less ϕ that is on 8 bits), thus a

precision of 1/1000.

The transmission is performed continuously, Ugen, Iex are read from 4 in 4 ms,

Istator , f and ϕ are read from 16 in 16 ms. Thus a succession of reading is presented as



follows: Iex, Ugen, Iex, Ugen, Iex, Ugen, I ex, Ugen, Istator (or Ugrid), Iex, Ugen , α , Iex, Ugen, Iex,

Ugen, a.s.o.

The forcing blocking circuit is made of solid-state circuit U2D. R75 is chosen so

that the voltage in pin 10 (Ugenerator) should be higher by 10% versus the voltage

from pin 11 (Ugrid) of U2D in the conditions in which the generator voltage and the

system voltage are rated values.

In case of a sudden short-circuit at the generator terminals, the voltage in pin 10

will drop far more than the system voltage (due to the reactance of the block

transformer) and the comparator U2D will oscillate from 0 in +5 V, the signal will be

processed by PLC.

The voltage equalization circuit is made inside the software inscribed in U3.

U3 compares the generator voltage (AN0) the system voltage (AN3) – a voltage

that is applied in AN3 only in open circuit through the relay K2 from the cabinet. At the

parallel operation on AN3 is applied the stator current.

If the generator voltage is higher than 0.9 V ( ¼ UNGen) and the system voltage is

higher than 2.5 V (0,7UNsist) then on the outputs 2RC3 or 2RC5 shall be given the order

to increase or decrease the reference to PLC according to the result of the comparison

by the software of AN0 with AN3.

When AN0 = AN3 ±1% 2, RC4 is 1 and gives the signal to PLC to allow closing I.O.

Measure circuit UE

The circuit for the measurement of the excitation voltage comprises the

electronic voltage adjustment board PACTC (U12) that reduces the excitation voltage

from 110V d.c. to 10V d.c. and transmits it to the voltage/current transducers U13, and

U14. U13 transmits the excitation voltage measure to the analogical input module U6.6

of the PLC; U14 transmits the excitation voltage measure outside to a hierarchically

superior system.

- BACKUP EXCITATION MEASURE CIRCUITS

In order to obtain the feedback of IE, the equipment receives:

- measure of the excitation current from the current transformers T6R, T7R -

75A/0.15A mounted on the alternative current circuit of the rectifiers (phase R and

phase T) in the diagram in V.

- MAIN EXCITATION REGULATORS CIRCUITS

The regulators that can be selected to function are cosϕ, Isinϕ, AVR or IEX (field

current regulator.

Circuits to form the set point value

The choice of the cosϕ, Isinϕ, AVR or IEX regulation working mode is

performed remotely or locally depending on the position of the selection key on the



equipment door. If it is selected the REMOTE CONTROL, the working modes can

from the control rooms through the relays KI5 for the cosϕ working mode, KI6 for the

IEX working mode or KI8 for Isinϕ working mode. If it is selected LOCAL

CONTROL, the working modes can from the operating panel through the key buttons

F8 for the cosϕ working mode, F9 for Isinϕ working mode, F7 for AVR working mode,

or F3 for the IEX working mode.

The value set point in every working mode is formed by the PLC. In theory it is

formed, as follows: in PLC there is a numeric register that represents the value set point

for the regulators from PLC. This may be set from O.P. between certain variations

limits.

The orders INCREASE, DECREASE are given from the control room through

the relays KI9, KI10 if REMOTE CONTROL is selected or from the operating panel

through the key buttons F6, F10, that modify according to the chosen working mode the

set-point register. The variation speed of the set points from minimum to maximum

may be set from the operating panel in the series 10…30 sec. (parameter of Set point

Variation Time).

Regulation and limitation circuits in AVR, cosϕϕϕϕ, Isinϕϕϕϕ working mode

These circuits are built inside the PLC.

- AVR (generator voltage regulator) type PI with ∆U/∆t forcing function

- cosϕ regulator

- Isinϕ regulator

- limitation of maximum stator current - The limitation occurs when the generator is

connected to the system and it is in lag working mode, as follows: when the stator

current exceeds the value K2xISN (K2 = 0.8....1.5 adjustable from O.P.), PLC starts to

compute the diagram (I2t) of the generator and after exceeding the time from the

diagram, the PLC modifies the regulator output, so that the stator current should drop

below the value of K2xISN for TLFS/IN (1...999 sec parameter adjustable from O.P.).

Also on the operating panel may be set the time for which the generator may debit the

double of the rated stator current (T = 0.1......9.9 sec)

- limitation for maximum excitation current - When the excitation current is more

than the 1.15 * Isn value, PLC begins to compute the diagram (I2*t) of exciter field and

when the time is more than the diagram’s time the PLC modifies excitation current

setpoint so the excitation current becomes IEXN. The IEXN is maintained a period of time

called TLFex/IN (1...30 min - adjustable parameter from O.P.).



- limitation of running in lead - the limitation occurs when the generator is connected

to the system and it is in lead working mode on the AVR regulator, as follows: The

maximum reactive power allowed for running in lead shall be computed according to

the active power with the following formula:

QM - Qm

Q* = QM - P x -------------- ,

Pn

where: Qm = values of running in lead at the active rated power; QM = values of running

in lead at the active power = 0 adjustable from O.P.

If the reactive power exceeds the value Q*, PLC modifies the regulator outputs,

so that the reactive should not exceed the value Q*.

- U/f correction - the limitation occurs in case the generator is running no load and the

generator voltage is higher than 20% from the rated value, as follows: When the

generator frequency drops below the value of Kfx50Hz (Kf = 0.5......0.9 adjustable

from PLC), the AVR output is modified, so that the relation UG/f should be constant

versus UGN/fN.

- limitation of the maximum voltage at the generator terminals accomplished by

means of the PLC operates, as follows:

- the limitation is accomplished by limiting the set-point register and by limiting the

regulator output at no load running.

- on tripping the generator switch breaker, remaining with the aggregate on no load

excited running, the PLC automatically brings the set-point register to the value at

which the parallel was performed.

Adjustment and limitation circuits in IEX working mode

The adjustment circuits in MANUAL working mode are also in PLC and

comprise the following adjustment loops:

- the excitation current regulator

- the limitation of the maximum excitation current accomplished by limiting the set-

point register and by limiting the regulator output at no load running.

- the limitation of the maximum generator voltage on tripping the generator switch

breaker, remaining with the aggregate on no load excited running, the PLC

automatically brings the set-point register to the value at which the parallel was

performed.



AVR - IEX switching

The switching from one working mode to another, as well as the monitoring

between the AVR and IEX working modes is described in Appendix PLC.

When the equipment is stopped, the switching is performed through the input

relays or the operator panel key buttons with no conditioning.

On receiving the switching orders, PLC displays on O.P. the selected working

mode and activates or deactivates the loops from PLC corresponding to the selected

working mode.

If the excitation equipment is started, the switching is performed as in the status

of stopped equipment with the following specifications:

- if it operates on AVR, cosϕ or Isinϕ the equipment through PLC it is immediately

switched on IEX (by observing the tracking) when the U5 board detects the " Generator

feedback voltage is missing " (IN13 = 1) or " Generator feedback current is missing "

(IN14 = 1).

- if it operates on IEX, it does not execute the order to switch to AVR, cosϕ or Isinϕ if

the board U5 detects the " Generator feedback voltage is missing " (IN13 = 1) or "

Generator feedback current is missing " (IN14 = 1).

- BACKUP EXCITATION CIRCUIT REGULATOR

Circuits for the formation of the set point value

The set point of the excitation current within the BACKUP excitation system may be

formed in two ways: analogical and numeric. The selection of the set point mode is

performed by means of the switch mounted on the door of the excitation equipment.

In the ANALOGICAL mode, the current set point is established by the operator

from the potentiometer mounted on the excitation equipment door and under the

NUMERIC working mode, through increase/decrease orders, locally from the operating

panel or remotely.

Regulation circuits

The set point value of the excitation current and the current feedback is transmitted

to the electronic board PRGL (U8R) that comprises the analogical current regulator in

PI configuration.

The output of the current regulator is the control voltage for the pulse generating

circuit to trigger the rectifiers, made of the U7R board of the DCGN type.

- THYRISTOR FIRING PULSES CIRCUITS

Circuit to form triggering pulses on gates

The MAIN excitation equipment has 2 identical pulse generating circuits -

electronic boards U7 - channel 1 and U8 - channel 2 of the DCGN type. The equipment

normally operates on channel 1. The equipment switches onto channel 2 in case of fault

of channel 1.



The BACKUP excitation equipment has 1 impulse formation circuit - electronic

board U7R of the DCGN type.

The DCGN block receives the following signals:

- 3 x Ualim thyristor bridge synchronization voltage in X1-2, X1-5, X1-8.

- 0 ÷ 5V (0 ÷2,5V – for the inverter working mode, 2,5 ÷ 5V - for rectifier working

mode) control voltage from the output of the regulator operational in X2-1, X2-2.

- 0V in X2-3 from A.P. – the order to block the pulses on stop and switching onto

channel 2.

- “inverter” order (+24V) in X2-4;

The DCGN block comprises:

- the circuits that form for the synchronization voltage rectangles of phase R, S, T made

of the transformers T1, T2, T3 and the integrated circuits U2A, U2B, U2C that

transform the input sinusoids from X1-2, X1-5, X1-8 (minimum voltage 30V,

maximum voltage 110) in synchronization rectangles with transits through 0 from

minus to plus with a delay of ~80.

- the device that generates the trigger pulses for the thyristors - the processor U3.

- the circuits that transmit the trigger pulses to the pulse transformers consist of the

transistor chain Q5-Q11

- the circuits that transmit the presence of the triggering pulses in the primary of the

pulse transformers to the processor U3 are made of the integrated circuits U5, U6, U7.

By the software the presence of the pulses in the primary of the impulse

transformers is monitored. An interruption of the pulse transformer primary, the

breakdown of a pulse way on the transistor chain Q5-Q11 is detected by U3 that

controls, in case of a breakdown, the transistor Q2 that transmits a fault signal.

If one of the synchronization phases is missing (F1, F2, F3 burnt out) or the high

speed fuses from the rectifier are burnt out, on Q3 or Q4, a signal is transmitted to the

PLC of the fault. If the synchronization frequency exceeds the limit 25Hz – 100Hz a

fault signal is transmitted again on Q3.

If the succession of the phases on X1-2, X1-5, X1-8 is not R, T, S, a fault signal

is transmitted on Q4.

Each of the boards U7, U8 has own pulse transformers, so that on the switching

from one channel to another there should be a 100%-redundancy in the thyristor firing

pulses circuit.

The circuit of transmitting pulses to the thyristors

The circuit of transmitting pulses to the thyristors accomplishes the adaptation of

the firing pulse parameters and the galvanic separation between the rectifier and the

impulse formation circuit.

This circuit is made up of pulse transformers planted on the electronic board

(U9) that is mounted on the rectifier with thyristors.



- PROTECTION CIRCUITS on the MAIN EXCITATION

The protection of the generator against over-voltage is ensured by PLC. The

trip threshold and the delay are adjustable from the operating panel (5 sec. after exiting

the parallel).

The protection of functioning with faulty rotating diodes is ensured by the

electronic board U5. This receives a voltage pro rata to the generator excitation voltage

from U4 conversion and galvanic insulation board (which has also role to separate the

rotor voltage of the generator from the control voltage in (24V)) and processes it in

view of detecting. When detected, the fault will be transmitted further to the PLC.

The protection against rotor earth fault is ensured by the relay U17 that

transmits the information to PLC.

The protection against excitation over-voltage of the exciter is ensured by

PLC. The trip threshold and the delay are adjustable from the operating panel.

The protection at the over-temperature of the MV transformer is

accomplished by means of relay U18 that transmits the information to the PLC.

The protection against the maximum excitation current of the exciter is

ensured by PLC. The trip threshold and the delay are adjustable from the operating

panel.

The protection against the minimum excitation current of the exciter is

ensured by PLC. The triggering threshold and the delay are adjustable from the

operating panel.

- DEVICES TO MONITOR AND DETERMINE PARAMETERS

The monitoring of the excitation system is accomplished by means of three

measurement devices:

P1 – excitation voltage

P2 – excitation current

P3 – static breaker test voltage.

The Operating Panel PV300 has been loaded with a program by means of which are

viewed and set the parameters of the excitation system.



1.5 Operating description

1.5.1 Controls on the Operating panel of the excitation equipment

Pressing

- F4 – the Main Menu appears

From the screen of the Main menu by typing:

-F2 → STATUS of the System

-F3 → Tests ( Static Breaker Test and Rectifier Test)

-F4 → setting Parameters (password “1122”; Protect Parameters have a special

password)

-F5 → Messages: Faults, Alarms

-F6 → Measures (electric measures)

-F7 → Local Commands (password “44”)

1.5.2 Tests

Rectifier Test

In the PLC program with the equipment stopped was provided an automatic

checking circuit of rectifiers that is initiated, as follows: on O.P. are pushed keys F4,

F3, F3, F2 if there are no faults in the equipment, the static breaker is disconnected, it

switches onto IEX, the pulses are enabled and the operator may control the increase and

decrease of the excitation current from the wanted value.

Throughout this period, PLC checks the condition of the rectifiers.

On pushing F3 after starting the test, the firing pulses channel 2 is enable and the firing

pulses channel 1 is disable.

On pressing on key F2 from O.P., the equipment is stopped by blocking the impulses

and connecting the static breaker.

Static Breaker Test

If the equipment is stopped, PLC enables the checking of the static breakers when a

control is given from O.P. for testing C.S. (pressing on F4, F3, F2).

- On pressing F2 – the test starts – at the terminals of the static breaker 24Va.c. is

applied and the voltmeter it shall indicate the voltage 20 - 24V.

Faults:

1. The voltage measured at P3 is 12V:

Possible causes: One of the thyristors is fault (short-circuit) or receives the control in

the gate (board U11 in fault or does not receive correct orders);

2. The voltage measured at P3 is 0V:

Possible causes: Both thyristors are in fault (short-circuit) or receive control in the gate

(board U11 in fault or does not receive accurate orders);



- On pressing F3 - the controlled thyristor V7 - P3 will indicate voltage 10-15V.

Faults:

1. The voltage measured at P3 is 24V permanent:

Possible causes: Thyristor V7 in fault; Thyristor V7 is not controlled - in fault on the

board U11 or presence of the order for V7 from PLC;

2. The voltage measured at P3 is always 0V.

Possible causes: Thyristor V8 in fault (short-circuit); the thyristor V8 receives the

permanent order - in fault on the board U11 or the presence of the order for V8 from

PLC;

- On pressing F3 - the thyristor is ordered V8 - P3 will indicate the voltage 10-15V.

Faults:

1. The voltage measured at P3 is 24V permanent:

Possible causes: Thyristor V8 in fault; the thyristor V8 is not controlled - in fault on the

board U11 or lack of control for V8 from PLC.

2. The voltage measured at P3 is always 0V:

Possible causes: Thyristor V7 in fault (short-circuit); the thyristor V7 receives

permanent order - in fault on the board U11 or absence of order for V7 from PLC.

- On pressing F3 - P3 it shall indicate the voltage 20 - 24V.

- On pressing F2 – the test is stopped.

At the control from O.P. for stopping the checking of the static breakers (F2 is clicked),

the stopping of the test is ordered by disconnecting 24 V a.c. and connection of static

breakers.

1.5.3 Messages

Messages on the MAIN EXCITATION

Messages are of three types:

- INT FLT: ** internal faults;

- EXT FLT: ** external conditions;

- WARNINGS: ** alarms;

Internal Faults

With excitation stopped - if any of the internal faults occurs the fault output relay will

be enabling and the excitation system will not start:

- RD temperature >80°°°°C; (there is a high current on RD due to the fact that the pulses

on the thyristors are not blocked or the thermal contact is in fault)

- Fault of measurement board; (BASC/RN – on AN1 U5 there is a voltage >0,7Vd.c.,

due to a residual current, that unblocks the protections or the U5 is in fault.

- PIC communication fault (fault on the conversion or the transmitting way for the

measures on the U5/U6- the excitation current signal, the generator voltage signal,

etc).



- Absence of one synch phase; (the absence of 1 synchronization phase is assessed on

both firing pulses channels)

- Absence of two synch phases or frequency over limits; (the absence of 2 or more

synchronization phases or frequency outside the limits 25Hz-100Hz on both firing

pulses channels)

- Overtemperature of excitation transformer; (the second stage of the temperature

protection occurred - if this protection is selected to be internal fault)

With excitation started/ generator no load - if any of the internal faults occurs the fault

output relay will be enable and the excitation system will trip







pulses channels)

- Fault of thyristor firing pulses (a fault of the thyristor firing way, is assessed on


- Absence 1 synch phase on PG1, fault on PG2;

- Absence 2 synch phases or frequency on PG1, fault on PG2;

- Fault of thyristor firing pulses on PG1, fault on PG2;





protection occured - if this protection is selected to be internal fault)

- Exceeding of fieldflash time (the generator voltage has not reached the value

0.5*Ugnom during the field flash time set on O.P.)

- Repetitive switch of firing channels (in 15 sec. were switched the firing pulses

channels from one to another for more than 5 times, loose links on both firing pulses

channels)


measures on the U5/U6- the excitation current signal, the generator voltage signal, etc)

- Maximum generator voltage exceeded (Ugen > threshold / t(s))

- Fault of rotating diodes; if this input signal is set as fault

With excitation started/ generator connected to the grid - if any of the internal faults

occurs the fault output relay will be enable and the excitation system will trip after

generator circuit breaker tripping:









pulses channels)

- Fault of thyristor firing pulses (a fault of the thyristor firing way, is assessed on









protection occured - if this protection is selected to be internal fault)

- Exceeding of fieldflash time (the generator voltage has not reached the value

0.5*Ugnom during the field flash time set on O.P.)

- Repetitive switch of firing channels (in 15 sec. were switched the firing pulses

channels from one to another for more than 5 times, loose links on both firing pulses

channels)


measures on the U5/U6- the excitation current signal, the generator voltage signal, etc)

- Maximum generator voltage exceeded (Ugen > threshold / t(s))

- Excitation current over limit (Iex > threshold / t(s))

- Loss of excitation current (Iex < threshold / t(s))

- Fault of rotating diodes; (when the electronic circuit from the U5 board detects fault

of the rotating diodes - open circuited or short circuited - if this input signal is set as

fault

Warnings:

- Commands switch breaker disconnected (Q2 disconnected)

- Incorrect working mode selection (the orders Isin – cos – AVR – MANUAL are in

the same time)

- Firing pulses fault on PG1 (fault of the triggering way for the thyristors on channel 1

board DCGN; it switched onto firing pulses channel 1 and immediately a firing pulses

fault was assessed on channel 1 )

- Absence 2 synch phases or freq. overlimit on PG1 (an high speed fuse on the

thyristors burnt out or a fuse from the channel 1 DCGN board or the frequency

exceeded the limits 25-100Hz)



- Absence 1 synch phase on PG1 (an high speed fuse on the thyristors burnt out or a

fuse from the channel 1 board DCGN)

- Firing pulses fault on PG2 (fault of the triggering way for the thyristors on channel 2

board DCGN; it switched onto firing pulses channel 2 and immediately a firing pulses

fault was assessed on channel 2)

- Absence 2 synch phases or freq. overlimit on PG2 (an high speed fuse on the

thyristors burnt out or a fuse from the channel 2 board DCGN or the frequency

exceeded the limits 25-100Hz)

- Absence 1 synch phase on PG2 (it switched onto firing pulses channel 2 and

immediately was assessed the absence of phase S or T; an high speed fuse on the

thyristors burnt out or a fuse from the channel 2 board DCGN)

When the alarms 3, 4, 5 or 6, 7, 8 occur on the active firing pulses channel the firing

pulses channel will be automatically switch the backup one (from one DCGN pcb to the

other pcb DCGN).

- Fault of rotating diodes (when the electronic circuit from the U5 board detects fault

of the rotating diodes - open circuited or short circuited)

- Generator feedback voltage is missing (if the voltage feedback for voltage regulator

or frequency measuring is missing)

- Generator feedback current is missing (if the current feedback is missing)

When alarms 10 and 11 occur the excitation system will be switched automatically to

the manual mode.

- 90 < PHY < 270 alarm (the PHY angle is outside measure limits)

- Rotor earth fault (the exciter field winding has an earth fault - if this protection is

selected to be an alarm )

External conditions

With excitation stopped - if any of the external conditions occurs the excitation system

will not start :

- Incorrect generator circuit breaker position; (the position of the generator circuit

breaker position is closed)

- Presence of stopping command; (the command to stop the excitation system is

present more than 3 seconds)

- Presence of tripping order by generator protections; (the excitation system was

stopped from generator protections or the stop command from generator protections is

present)


protection occurred - if this protection is selected to be external condition)

With excitation started:

- Rotor earth fault (the exciter field winding has an earth fault - if this protection is

selected to be external condition )



If Overtemperature of excitation transformer or Rotor earth fault occur, the fault

output relay will be enable and the excitation system will trip after generator circuit

breaker tripping ;

If Presence of stopping command and Presence of tripping order by generator

protections occur when the generator is connected to the grid the excitation system

will not stop until the generator circuit breaker is disconnected.

1.5.4 Commands

MAIN EXCITATION and BACKUP EXCITATION are selected by means of key

SBR

SBR on position 1 - selects MAIN EXCITATION

SBR on position 2 - selects BACKUP EXCITATION

a. MAIN EXCITATION SELECTED

START-UP

The supply of the equipment may be performed from the generator terminals or from

the internal services of the power plant. The selection of the supply source is performed

by means of the SAL key: on position 1 supply from the generator stator; on position 2

supply from internal services. The selection of the supply source shall be performed

with the equipment stopped and it shall not change in operating.

From the REMOTE/ LOCAL selector switch it can be chosen the way that the

excitation will be controlled: remotely from UCB or locally from the Operating Panel;

the position of the selector switch can be changed any time.

The equipment starts on receiving the order start (excitation of relay KI-2 permanent or

key button F2) if:

- there are no faults in the excitation equipment

- no order for Rectifier Test or Static Breaker Test is given

- minimum 10 sec elapsed from the last stop.

- there is speed signal > 90% (excitation of relay KI-11 permanent)

The PLC breaks of the order from the thyristor gates from the static breaker and

enables the triggering pulses for the rectifier bridge.

If the cosϕ or Isinϕ working mode is selected, until the generator will be connected to

the grid the working mode will be AVR.

Regardless of the chosen working mode, the start-up of the equipment is performed

under IEX working mode.



- If the supply is selected from the generator stator, after the occurrence of the start-up

order, the excitation winding is supplied with direct current from the power plant

battery by closing relay KA until the generator voltage exceeds the value 0,5*Ugnom.

When the generator voltage exceeded this value, the field flash breaker is de-energized.

The excitation starts with a start-up set point (Start-up manual) different from 0, so that

the field current should generate minimum 0,5*Ugnom. Then according to the initially

chosen regulation working mode (IEX or AVR), the equipment remains at the initial

current value (in IEX working mode) or it shall increase the excitation current until a

set point AVR start-up and then it switches to the AVR working mode and the voltage

of the generator is equalized with the one of the system in view of synchronization.

- If the supply is selected from the internal services of the power plant, after the

occurrence of the start-up order, the set point of the excitation current shall have the

value set in the operating panel: according to the initially chosen regulation working

mode (IEX or AVR), the equipment is excited at the start-up value set as a reference

from the operating board, respectively IEX start-up (adjustable between 0 and 50%In)

in IEX working mode or it shall increase the excitation current until a set point AVR

start-up, and then it switches on to the AVR working mode.

In the IEX working mode, the excitation system will control the field current of

the exciter. The current set point may vary between the values of minimum and

maximum current at no load running set in the operating panel.

In AVR working mode, excitation system will control the generator voltage. The

voltage set point may vary between the values of minimum and maximum voltage at no

load running set in the operating panel.

The variation time of the excitation current set point on start-up is established

according to the incremental quantum.

The variation time of the set points from the minimum to the maxim value is

established in seconds from the operating panel.

By the PLC program until the connection of the generator to the system is activated the

“forcing limitation".

If the absence of the generator voltage measure is detected, it switches on the IEX

working mode and it shall not be allowed to switch on to the AVR working mode.

If the AVR working mode is selected and the frequency decreases below an adjustable

value in parameters, the voltage set point is modified, so as to keep constant the U/f

relation.

In the IEX working mode, after closing the generator switch, the operator varies

the current set point in order to load with reactive power the generator.

In AVR working mode, after closing the generator switch takes place an

automatic charging with reactive power until an adjustable value (the power factor is

set) and then the equipment remains in the wanted working mode (voltage regulator or



reactive power regulator or power factor regulator) and the operator may establish the

operating point.

The set point varies between the minimum and maximum limits at parallel

running set in the operating panel.

In AVR working mode are also active the following functions:

The operating in lead working mode is limited according to a linear characteristic

P=f(Q) ( subroutine SMQC).

If the stator current exceeds an overload value set in OP, the operating time at the

measured current shall be limited according to a thermal characteristic I2t (subroutine

SCMS)

If the excitation current exceeds the value 1.15 In, the operating time at the

measured current shall be limited according to the thermal characteristic I2t (subroutine

SLF).

In cosϕ and Isinϕ working modes is active only the SCMS subroutine.

The resuming of the no load running is performed by tripping on the generator switch

breaker. According to the actual operating working mode shall take place the

following:

Irrespective of the operating working mode, unless activated the function of

resuming zero at the set points, the current set points and the voltages are brought to the

actual value at the moment of connecting the generator to the network on IEX or AVR

working modes.

If the function of the set points of resuming zero is activated in the IEX working

mode, the excitation current set point will drop to the “minimum set point in the

MANUAL working mode”.

If the function of resuming zero at the set points is activated (see the program

PLC - STZ) in AVR working mode, the set point of the excitation current will decrease

from the “minimum set point in the IEX working mode” to a time interval adjustable in

OP and then shall be resumed the start-up process in AVR working mode.

The equipment normally operates on firing pulses channel 1. At the absence of R

or S, T for more than 3 sec or a "firing pulses fault GI 1", the equipment starts/switches

to firing pulses channel 2 if this is operational.

STOPPING

The stopping of the excitation equipment is performed in 3 ways:

- normal stop (at external order – excitation of relay KI3 or key button F4)

- generator protection (at the external order - excitation KI4)

In AVR with the generator connected to the system, after receiving the stopping order,

the reactive power is brought to Q<5%.



After confirming that I.O. is disconnected, PLC orders the sending of the firing pulses

angles into the inverter for approximately 3 sec, after which the connection of the static

breaker and the blocking of the impulses on the thyristors from the bridge is ordered.

- stopping of the excitation equipment by fault

On stopping from faults after confirming that I.O. is disconnected, the pulses are

blocked and the static breaker is ordered directly.

NOTE: The equipment can restart only after 10 sec from the last stop.

b. BACKUP EXCITATION SELECTED

START-UP

From the REMOTE/ LOCAL selector switch it can be chosen the way that the

excitation will be controlled: remotely from UCB or locally from the Operating Panel;

REMOTE CONTROL selected – orders from UCB:

The equipment starts on receiving the order start (excitation of relay KIR-2 permanent)

if:

- there are no faults in the excitation equipment

- there is speed signal > 90% (excitation of relay KIR-11 permanent);

The current set point is varied from the PLC by using the orders increase and decrease

from UCB.

LOCAL CONTROL selected:

The potentiometer must turned on the 0(minimum) position.

The equipment starts on receiving the signal speed > 90% (excitation of relay KIR-11

permanent) if:

- there are no faults in the excitation equipment;

The current set point is varied using the potentiometer from the equipment door.

Changing the position of the REMOTE/ LOCAL selector switch on the BACKUP

excitation the fault output will be enabled.

STOPPING

The order of intentionally stopping (the excitation of relay KIR-3) or the stopping order

from the generator protections (the excitation of relay KIR-4) is stopping the excitation

only after opening the generator circuit breaker. The pulses are blocked and the static

breaker is controlled. The order of intentionally stopping cannot be performed on the



LOCAL CONTROL. A stop signal can be forced, meaningly changing the position of

the REMOTE/ LOCAL selector switch.

If the control is remote, the set-point decreases to 0 after the generator circuit

breaker trips.

If the control is local, the operator must turn manually the potentiometer to zero.

A backup excitation fault enables the fault output and the stopping order from the

generator protections will stop the excitation system.



CHAPTER 2 – INSTRUCTIONS OF COMMISSIONING

2.1 Necessary documentation

In order to commission the static excitation equipment, the product “INSTRUCTIONS

FOR OPERATION AND MAINTENANCE” are necessary together with the attached

drawings.

2.2 Measurement devices necessary for setting into operation and adjustment

- Oscilloscope with 2 spots, memory and probes for reducing the voltage

- Digital multimeter

- insulation resistance: min. 1 MΩ - 4 digits

- measurement range: 0,1 V - 500 V

- Universal measurement device

2.3 Setting the equipment into operation

ATTENTION!

1. The personnel ensuring the setting into operation, repair and operation of the electric

equipment should have a training and labor protection sheet according to the effective

norms and they are under the obligation to know the equipment and the content of the

Instruction for operation and maintenance of the equipment.

Before the supply, the earthening link shall be checked.

Rubber carpets are provided in front and in the rear of the equipment.

The testing and checking of the pulses for the firing of the thyristors shall be performed

by using an oscilloscope supplied mandatory from the plug without protection contact

supplied from the separator transformer.

2. This chapter comprises the works for the setting into operation of the equipment after

the deliver from ICPE ACTEL or after a major repair of the equipment (replacement of

electronic block, thyristors, current and voltage transformers, etc.).

2.3.1. Preparing checking for commissioning.

2.3.2. Checking of the MAIN static excitation equipment.

2.3.3. Checking of the BACKUP static excitation equipment.



2.3.1. Preparing checking for commissioning

Before supplying the equipment with voltage, a visual inspection is necessary that aims

at:

-equipping the product with component elements according to the gear specification

-checking the accuracy of the links of the equipment with the outside, to the

generator and in the automation of the power plant

-checking the correct tying of the force links, as well as of the cable sections

-checking the non-occurrence of modifications during transport and mounting

operations.

Checking the power supplies

The equipment is supplied with:

• 3 x 415V +N a.c./5A in clips XI.R,S,T,N – ac service supply

• 110V d.c. in clips X.+BAT and X.-BAT – supply of battery for field flash

• 110 V d.c./5A from the battery of the power plant:

terminal + in clip X-53;

terminal - in clips X-52;

• +24V at source U1 in terminals +24/0V;

• +24V at source U2 in terminals +24/0V;

• +24V at source U3 in terminals +24/0V.

2.3.2. Checking the MAIN excitation equipment

Turn the cam switch SBR to position 1 to select the MAIN excitation.

The switch breaker Q1 are closed to transmit the voltage of 24V d.c. to the supply bars

BA.0V, BA.24V and Q2 to supply the commands relays with 110V d.c.

Wait until O.P. displays the absence of ±24Vcc. Click on F1. As of this moment U6.I∅

÷ I 7 (PLC) should flash intermittently and on O.P. should be displayed the main

screen.

If I∅ ÷ I 7 do not flash, U5 or U6 are in fault.

1. Checking the static excitation equipment on the generator excitation with

non-spinning rotor.

- Checking the synchronization

- Preparation: the connections are untied from the firing pulses circuits on the

thyristor gates.

- The ac service supply is coupled, the SAL key on position 2 and Q3 is closed;

- The IEX working mode is chosen. The RECTIFIER TEST start order is given. The

enable of the firing pulses signal corresponding to channel 1 is observed –

turning on the green LED U7.



- The presence of the pulses on the thyristors is checked, as well as their correct

synchronization, as follows:

With an oscilloscope are viewed the wave forms between the cathode-gate at each

thyristor, connecting the hot terminal of the oscilloscope to the gate of the thyristor.

They should have the shape:

Their amplitude is variable between 1V and 6V according to the internal

resistance GK of each thyristor.

For thyristors with common cathode V1, V3, V5 the impulses should be

positioned versus their phase voltage, as follows:

Remarks

1. The phase shall be oscillographed by using a separation transformer connected

between the concerned phase and null.

2. The oscilloscope shall be connected as follows:

- probe 1 + is connected to the polarized terminal of the separation transformer on

the secondary part;

- probe 2+ is put on the gate of the thyristor;

- the tables of the oscilloscope terminals are connected to the separation

transformer 0V on the secondary part and the thyristor cathode.

For thyristors with common anodes V2, V4, V6, the impulses should be versus the

voltage of their phase, as follows:



- The stopping of the excitation is ordered.

- The movement by 60° electric to the right of the impulses on the thyristors (the

inverter working mode) is checked for approximately 3 sec and then the impulses

should disappear simultaneously with the control of the static contactors (2OUT1=0

and 2OUT3=1 from U6.2).

The above operations are executed for both regulation channels.

- Protection checking

After simulating a fault or a malfunction, it is necessary to reset the equipment remotely

or from the operating panel of PLC by the key F1.

· (Absence of phase R or limit f) or (absence of phases S or T) channel 1 -

malfunction

One or more of the fuses F1, F2, F3 is removed from U7.

- the LED 1IN1 or 1IN0 flashes on U6.1.

- the firing pulses of the thyristors is switched onto channel 2; the LED OUT.0 from U6

is turned off and the LED OUT.1 on U6 is turned on

- on the operating panel is displayed the message DF

· (Absence of phase R or limit f) or (absence of faze S or T) channel 2 - malfunction

One or more of the fuses F1, F2, F3 is removed from U8.

- the LED 1IN4 or 1IN3 on U6.1 is turned on.

- the firing pulses of the thyristors is switched onto channel 1; the LED O.1 from U6 is

turned off and the LED O.0 from U6 is turned on

- on the operating panel is displayed the message DF

· Firing pulses fault on GI1

The wire X3-3 is removed from U7 with the turned on equipment.

It is assessed that 1IN2 from U6.1 is turned on for a short while and then O.0 is turned

off and O.1 is turned on from U6 and the fault message appears.

· Firing pulse fault on GI2

The wire X3-3 is removed from U8 with the turned on equipment.

It is assessed that 1IN5 from U6.1 is turned on for a short while and then O.0 is turned

on and O.1 is turned off from U6 and the fault message appears.

- Checking the static breakers

With the equipment turned off, from O.P. is ordered the checking of the static

breakers.



- Checking remotely orders and signaling

The selector switch REMOTE/ LOCAL should be on the REMOTE position

The following shall be checked:

1. the equipment receives all orders from the control room

2. the equipment receives information from the position of the generator circuit

breaker.

3. the equipment receives a stopping order from the generator protections and

turbine.

4. the equipment sends correct signals to the control room

- Checking the rectifier and the thyristors firing pulses generator boards

The connections between the output terminals of the excitation (1X.1 and 1X.2)

and the excitation of the generator are checked. (ADR is closed if exist).

The IEX working mode is chosen. The RECTIFIER TEST start order is given.

The enable of the firing pulses signal corresponding to channel 1 is observed – turning

on the green LED U7.

The order INCREASE is given, aiming to increase the voltage on the voltmeter

P1 from the equipment door for no more than ½ *UN EXC. The order DECREASE is

given, aiming to decrease the voltage on the voltmeter P1 from the equipment door

towards 0.

The order normal STOP is given. The turning off of the rotor field is aimed at.

- Tunning of the current feedback level

The RECTIFIER TEST start order is given. The button INCREASE is activated

until the set point displayed on the operating panel shows 50%. The level of the

excitation current feedback measured on the shunt (or on the ammeter) should be of

50%In. If the case may be, adjust the level from the potentiometer P1 from U5. The

order DECREASE is given until the minimum.

NOTE: All adjustments or modifications from O.P. should be performed by personnel

that know the implications of the modifications very well.

2. Checking the static excitation equipment on the generator, running no

load

A. Select the supply from the internal services of the power plant –SAL can switch

is on the position 2.

Adjusting the current regulator under IEX working mode

The generator is excited under IEX working mode up to 90% from the rated voltage of

the generator.



The amplifying factor of the main current regulation PLC is adjusted, as follows:

- the regulator is put in P (TIM = 0.001 is set)

- on the entry of the regulator are applied small perturbations 1-2%

- the KRM amplification is increased until the oscillation limit

- the amplification of the KRM regulator is established at 1/2 from the value at which

the oscillation occurred

The integrating factor of the current regulator is adjusted, as follows:

- TIM maxim (0.99) is inserted

- gradual signals are applied and the feedback of the regulator is monitored, aiming to

obtain an over-adjustment of maximum 10% by modifying TIM.

Determination of the feedback level of UG

With the excitation on IEX, the equipment is excited until the rated voltage of the

generator.

It is checked that on the board U5 pin 2 circuit U3 (processor), there is a voltage

of 3.6 Vdc; if not, it is adjusted from R26 of board U5.

The presence is checked in clips X-8 for phase R, X-9 for phase S, X-11 for

phase T of the voltage feedback on the terminals (approximately 3x100Vac/

3x110Vac).

Checking the regulator UGmax IEX working mode

The order is given to increase the reference continuously and it is assessed that

the voltage on the terminals does not exceed 1.2*UNG by limiting the maximum IEX

set-point.

Set the field current level for startup on AVR working mode and startup with

fieldflash

Decrease the field current in order to decrease the generator voltage to 85%

UGnom. The value of the excitation current in percents is put as the “Startup current on

AVR”

Decrease the field current in order to decrease the generator voltage to 50%

UGnom. Now the parameters of “Minimum current set-point” and “Fieldflash startup

current set-point” can be set.

The adjustment of the regulator of UG AVR

The function of voltages equalizing is disabled.

With the excitation on IEX, the equipment is excited until the rated voltage of the

generator.

The excitation system is witched from IEX to the AVR working mode. The

amplification factor of the voltage regulator is adjusted from O.P. – KRA and the

integration time TIA – the same way as the current regulator was adjusted.



Checking the regulator UGmax AVR working mode

The limiter UGmax on AVR is ensured by limiting the maximum AVR set-point.

Checking the monitoring and switches AVR - IEX

The generator is excited at a voltage comprised between 0.8...1.1 UGnom. The

order to switch between IEX/AVR working modes and vice-versa is given. The

switching should be performed without a shock in the excitation current. The condition

that the excitation equipment should operate in AVR working mode is that the

generator voltage (measured in clips x-8, x-9, x-10) should exceed the threshold of 0.8

rated Ugen.

BkS at no load running (Backup Supply - if ac service has to power supplies

that can be switched during excitation functioning)

ON notifying BkS (1IN0=1 or 1IN1=1 and 1IN3=1 or 1IN4=1), if:

- it is operating under IEX working mode, the constant excitation current regulator

takes the value of “Limiting the Current Regulator BkS -5V - +5V” for “Time to

Memorize BkS on Manual” and then until “Time of Memorizing BKS on

Manual” the regulator will operate within the margin “Limitation of Manual

Regulator BkS -5V - +5V” ± a value adjustable from the computer and then the

regulator is released from the BkS limitations;

- it is operating under AVR working mode, the program for the constant excitation

current regulator shall perform the same program as on operating under a IEX

working mode; additionally, the constant voltage regulator Ugen shall take the

value of “Limiting the Voltage Regulator BkS 0-5V”. For the “Time to

Memorize BKS on Automatic” and then the regulator is released from BkS

limitations.

Attention! If for 3 sec. the supply voltage of the excitation force does not appear again,

the excitation equipment shall control the triggering of the group. On O.P. shall appear

the message: “Absence of phases S or T” and “Absence of phase R or limit f”.

Remark: On BkS in parallel, regulators have no limitations. The BkS break is accepted

for maximum 3 sec.

Checking the correction of U/F

The generator frequency decreases below 48 Hz with the excitation on AVR until

the rated voltage.

It is noticed when the voltage at the generator terminals start to decrease

(between 46...48Hz). By means of the computer is established the weighting of the

correction.



Checking the starting of the excitation system on AVR working mode

Select the AVR working mode. Start the generator and the excitation system. The

generator voltage should be increased to a value between the minimum and maximum

AVR set-points set on the operating panel.

B. Select the supply from the internal services of the power plant –SAL can switch

is on the position 1.

Checking the starting of the excitation system on AVR working mode, using

generator stator voltage

Select the AVR working mode. Start the generator and the excitation system. First

exciter field circuit will be supplied from the battery voltage. After the generator

voltage is built up to 50% UGnom, the rectifier uses this voltage to build up the

generator voltage to the synchronizing value.

3. Checking the static excitation equipment on the generator operating in

charge (coupled to the system)

The IEX adjustment working mode is selected.

- Adjustment of the reactive power feedback Q and the active power P

The generator is excited; it is synchronized with the system and it is coupled to

the system.

The generator is charged at P = 1/3*PN and Q = 1/3*QN.

The stator current feedback measure is checked. The displayed value on O.P.

(percentage from rated value for stator current) must indicate a correct value. If any

errors appear, an adjustment on the electronic board BASC can be made: P2

potentiometer (if there is a big error then operator must verify connection mode for

wires in clamps X1, X2, X3 and, if needed, change R39 and R40 from U5- BASC:

(R39 in parallel with R40) ↑ than P.V. displayed value ↑ - any changes for resistances

are made with motor and excitation equipment stopped and with Q1 opened).

The power factor measure is checked. If the displayed value on O.P. is not a

correct value the followings can be done:

- modify potentiometer P3 on the U5 – BASC board

- change the condenser C10 with one that has a lower value to increase the angle

value or with one that has a higher value to decrease the angle value;

- modify P.V. parameter "CORRECTION PHY" (screen 43) – the correction factor

is the amount of degrees needed to be added or subtracted multiply with 2,

positive or negative;



The P and Q measure is checked. Use, if it is needed, the cosϕ and sinϕ

correction parameters on the O.P. to display the correct values

The MAIN excitation can be further switched onto AVR or cosϕ or Isinϕ. On AVR the

device is charged with active power until PN aiming that Q remains approximately

constant at 1/3*QN, without giving orders to INCREASE-DECREASE the excitation on

the door of the equipment cabinet.

If the reactive variations are higher, they are adjusted from KST-O.P.

2.3.3. Checking the BACKUP excitation equipment

Turn the cam switch SBR to position 2 to select the BACKUP excitation.

The switch breaker Q1R are closed to transmit the voltage of 24V d.c. to the supply

bars BAR.0V, BAR.24V and Q2 to supply the commands relays with 110V d.c.

If the relay KE3 is switched off, the relay K1R will be switch ON.

1. Checking the static excitation equipment on the generator excitation with

non-spinning rotor.

- Checking the synchronization

- Preparation: the connections are untied from the firing pulses circuits on the

thyristor gates.

- The ac service supply is coupled and Q3 is closed;

- Switch the REMOTE/LOCAL switch to LOCAL

- Simulate the 90% speed signal and the firing pulses will be enabled.

- The presence of the pulses on the thyristors is checked, as well as their correct

synchronization, as follows:

With an oscilloscope are viewed the wave forms between the cathode-gate at each

thyristor, connecting the hot terminal of the oscilloscope to the gate of the thyristor.

They should have the shape:

Their amplitude is variable between 1V and 6V according to the internal

resistance GK of each thyristor.

For thyristors with common cathode V1, V3, V5 the impulses should be

positioned versus their phase voltage, as follows:



Remarks

1. The phase shall be oscillographed by using a separation transformer connected

between the concerned phase and null.

2. The oscilloscope shall be connected as follows:

- probe 1 + is connected to the polarized terminal of the separation transformer on

the secondary part;

- probe 2+ is put on the gate of the thyristor;

- the tables of the oscilloscope terminals are connected to the separation

transformer 0V on the secondary part and the thyristor cathode.

For thyristors with common anodes V2, V4, V6, the impulses should be versus the

voltage of their phase, as follows:

- The stopping of the excitation is ordered.

- The impulses should disappear simultaneously with the control of the static

contactors.

The above operations are executed for both regulation channels.

- Protection checking

· (Absence of phase R or limit f) or (absence of phases S or T) channel 1 -

malfunction

One or more of the fuses F1, F2, F3 is removed from U7R.

The K6R relay is switched on.

· Firing pulses fault

The wire X3-3 is removed from U7R with the turned on equipment.

The K6R relay is switched on.

· REMOTE/LOCAL selection switch wrong position

The REMOTE/LOCAL selection switch changes its position after the BACKUP

excitation was started.



-Tunning of the current feedback level

Simulate the 90% speed signal and the firing pulses will be enabled. Increase the

field current using the potentiometer, turning it to the maximum. The maximum field

current must be 1.1In.

NOTE: All adjustments or modifications should be performed by personnel that know

the implications of the modifications very well.

Adjusting the current regulator

Simulate the 90% speed signal and the firing pulses will be enabled.

The amplifying and integrating factors of the current regulator are adjusted, as follows:

- change the value of the R6 resistor and the C1capacitor on the U8R board until on a

set-point step, the reaction of the regulator has an over-adjustment of maximum 10%

and 3 quivers around the output steady value.



CHAPTER 3 – REPAIR INSTRUCTIONS

The necessary documentation and the devices are the ones from chapter 2 –

setting into operation.

No. Manifestation of

fault Possible causes Remedy

1 The equipment

does not start

- the READY conditions are

not fulfilled

- the STOP order is present

- the equipment has not been

reset after a fault stop

- check whether there are

STOP orders

- the breakdown messages are

checked from the operating

panel

- the presence of the force

voltage at the rated value is

checked

2 The excitation

equipment starts,

but does not react

to the

INCREASE order

- the breakdown of the way

to transmit the order

INCREASE from the control

room up to the level of the

PLC

- the breakdown of the

regulation way and its

sending to the thyristors

- check the switching on of the

relay KI9

- check the turning on of LED

1IN14 from U6.1

- check the blocks DCGN –

U7, U8

- check the presence of the

order to enable the pulses from

DCGN board

- check the transmission of the

pulses from DCGN through

the firing pulses circuits to the

thyristor gates

3 The excitation

equipment

generate high

excitation current

on start-up

-absence of the UG or Ie

feedback for the start-up

under the AUTOMATIC or

MANUAL working mode

- fault of DCGN boards

- check whether the set point

voltage measured in terminal

X2-1, X2-2 of U7, U8 boards

is the minimum value

(0÷2.5V)

- check the presence of the Ie

feedback (excitation current)

and of the Ug feedback

(voltage in the terminals) on

U5-BASCRN.

- check the DCGN boards



4 The excitation

equipment has

excitation current

variations without

the order

INCREASE or

DECREASE

- the presence of imperfect

contacts on the way of the

set point, adjustment and

transmission to the thyristors


contacts on the way to form

the Iex feedback – excitation

current


contacts on the way of

forming the UG or Q

feedback for the

AUTOMATIC working

mode

5 The excitation

current cannot be

varied in the

entire wanted

series

- the modification of the

variation series of the set

points


values of the feedback

measures


established values from O.P.

- the disappearance of a

firing pulse

- the settings from O.P. are

checked

- the presence of all firing

pulse are checked

6 The excitation

equipment

switches from the

AUTOMATIC

working mode to

the MANUAL

working mode

- fault : generator

feedback voltage is

missing

- fault : generator

feedback current is missing

- the voltage measure is

checked from the measure

board BASC.

7 The excitation

equipment stops

without the

intentional STOP

order

- fault of the excitation

equipment

- STOP by generator or

turbine

- the presence of fault

messages on the operating

panel of PLC is checked

- the presence of the STOP

order is checked



CHAPTER 4 – INSTRUCTIONS FOR MAINTENANCE

4.1 Daily inspection

During the operation, the following are checked on a daily basis:

- the noise caused by the equipment during operation

- the messages on the operating panel of the PLC on the cubicle door

- the indications of the measurement devices.

4.2 Periodic inspections and checking

The static excitation equipment needs periodic revisions (at least once every 6 months),

when the following operations are executed:

- cleaning the cabinets of dust. The blowing with dry air jet at 2 atm. is executed. They

shall execute the blowing with dry air jet at 2 atm. They shall especially insist on the

clip row, the plugs of the relays, and the radiators of the thyristors. The electronic

blocks shall be blown from a distance of minimum 50 cm.

- the electric and mechanic checking of the earthing links;

- the correct screwing of the connections to the from the clip row and the links from

the force circuits;

- checking the correct screwing of the assembly screws of the subassemblies; checking

the mechanical insurance of the relays through the concerned blocking bridles;

- checking the mechanical blocking of the electronic boards;

- a visual inspection upon all subassemblies is executed, aiming at tracking faults; the

components that are in fault condition or unsafe in operating are replaced;

- the components that are galvanic covered and the components that present corrosion

of the basic material shall be replaced;

- the components covered by painting are examined and the components that present

corrosion of the basic material are repainted;

- the normal operation of the fans is checked

At least once a year the following electric checking activities are executed:

- checking the supply sources

- checking by simulation all protections and signaling

- checking the proper operating of the static contactors by means of the checking

circuit from the cabinet

- checking the set point measures of PLC under AVR and IEX working mode

- checking the value of the feedback measures from the adjustment: the voltage at the

terminals, stator current, excitation current, active power, reactive power, frequency

- checking the thresholds of the limitation regulators under AVR and IEX working

mode

- orders of START-STOP, INCREASE-DECREASE, AUTOMATIC-MANUAL are

given with the equipment not coupled in charge.

SRATN Operating Manual

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Transcript of SRATN Operating Manual