Sel1 Hv Switchboards

Atelier Management and Design Consultancy (Vietnam) Co.,Ltd SEL1-HV SWITCHBOSRDS/1

SECTION 1: HV SWITCHBOARDSSECTION 1: HV SWITCHBOARDS

1.1 GENERAL

1.1.01 Functional description

The Medium Voltage Switchboards Scope of Works includes the detailed design, engineering, workshop drawings preparation and approval, manufacturing, factory testing, supply, delivery, installation, testing and commissioning and finally handover to the Employer of the Medium Voltage Switchboards rated as shown on the relevant drawing in the framework of entire project completion as indicated on the relevant drawings.

1.1.02 Cross references

Workstation General Requirements

Workstation Electrical & Control Systems General Requirements

Medium Voltage Switchboards

Distribution Transformers

Power Cables

1.1.03 Standard

General

The Medium Voltage Switchboards shall comply with the lastest issues of the following IEC recommendations:

IEC 60056 High Voltage Alternating Current Circuit Breakers

IEC 60129 High Voltage A.C. Switchgear and controlgear disconnectors (isolators) and earthing

IEC 60185 Current transformers for measurement and protection.

IEC 60186 Voltage transformers for measurement and protection.

IEC 60265-1 High voltage Switch for rated voltages above 1 KV and less than 52 KV

IEC 60298 AC Metal Enclosed Switchgear and ControlGear for Rated Voltages above 1 kV and up to and including 54 kV.

IEC 60282-1 HV fuses

IEC 60420 High voltage a.c. Switchgear and control gear – switch - fuse combinations.

IEC 60529 Degrees of protection provided for enclosures (IP Code).

IEC 60605 Approval and test specification – general requirements for electrical equipment.

IEC 60694 High voltage a.c. Switchgear and control-gear-circuit breakers for rated voltages above 1000V.


1.1.04 Design

General

The Medium Voltage Switchboards shall be designed in accordance with the above-mentioned standards, and applicable drawings.

The Medium Voltage Switchboards shall be capable of continuous duty at rated voltage/frequency stated in this Specification.

Technical Parameters

Rated voltage – 24 kV

Operating voltage – 15 kV (existing)

Operating voltage – 22 kV (future)

Frequency – 50 Hz

Rated power frequency withstand voltage - 50 kV - 50 Hz, 1 min

Rated lightning impulse withstand voltage - 125 kV - 1,2/50 µs

Rated short-circuit breaking current - 25 kA - 3 s

Rated short-circuit making current - 60 kA

Busbars rated current – 1250 A

The auxiliary supply voltage shall be 110 V DC with a permissible variation range of -15% to +10%.

Incoming/Outgoing CB’s shall be rated – 1250 A – two units

Distribution Transformers CB’s shall be rated – 630 A – two units

Service conditions

The Medium Voltage Switchboards shall be suitable for installation and operation in Vietnam and the environmental conditions described in the data sheets and project specifications.

The manufacturer shall be responsible for ensuring that all equipment and components supplied are suitable for the operation and conditions stated. Where the manufacturer standard or preferred design option does not meet the operation or environmental conditions, the manufacturer shall give details of the technical changes and commercial impact of complying with the stated conditions.

The Medium Voltage Switchboards shall be designed for ambient temperature of 40ºC.

Safety and Reliability

The Medium Voltage Switchboards shall be designed to minimise any risk of an internal short circuit and shall be of metal clad design. In the event of any internal arcing fault on a functional unit, the damage shall be confined to that unit so that the busbars and all other functional units are undamaged and operational.


The Medium Voltage Switchboards design shall incorporate arc fault containment features. The level of arc containment test to which the switchboard complies shall be stated and any required features (e.g. vent flaps) shall be identified.

The Medium Voltage Switchboards shall be designed in such a manner that all components shall be operated and maintained safely and shall not present a hazard to personnel or cause damage to other equipment.

The metal enclosure shall be hermetically sealed and “safe to touch”.

All MV and internal drive parts shall be maintenance-free for at least 10 years or 10 000 mechanical operations.

Switchgear shall be arc-fault tested

Submission

The Contractor shall submit for the Engineer’s approval the following workshop drawings and calculations:

Single Line Diagram

Protection Diagram

Calculation of prospective relay settings

Types, model numbers and ratings of assemblies.

Detailed dimensions.

Shipping sections, general arrangement, plan view, front elevations and cross-section of each compartment.

Projections from the assembly that may affect clearances or inadvertent operation, such as handles, knobs

Fixing details for floor or wall mounting.

External and internal paint colours and paint systems.

Construction and plinth details, ventilation requirements

Engraving Mimic Diagram

Manufacturer’s name

Type designation

Purchaser order number

1.2 QUALITY

1.2.01 Switchboards type

The Medium Voltage Switchboards shall be indoor type unit designed with the minimum acceptable degree of ingress protection (IP) for electrical equipment and devices shall be as IP2x.

The Medium Voltage Switchboards shall be free-standing, floor mounted, and all switching operation shall be carried out from the dead-front operating panel.


Live line test facilities shall be available on the panel front.

Drive mechanism and current transformers secondary circuits shall be freely and safely accessible.

1.2.02 Functional units

Medium Voltage Switches

The Medium Voltage Switches shall use low pressure SF6 gas or vacuum for current interruption and shall require no maintenance. The Medium Voltage Switches enclosure shall be mounted horizontally within the cubicle and the position of the main and earthing contacts shall be clearly visible from the front of the cubicle. The position indicator shall be placed directly on the contact operating shaft.

The Medium Voltage Switches shall be of the high operating frequency type in accordance with paragraph 3.104 of IEC 60265-1 recommendations. They shall have three positions (closed, open and earthed) and shall be fully assembled and tested before leaving the factory.

The Medium Voltage Switches shall have a service life of at least 30 years. No refilling of the gas or vacuum creation shall be required over this period.

The mechanical endurance of the switch operating mechanisms shall ensure at least 1000 operations.

Circuit Breakers

The Medium Voltage Circuit Breakers shall be of the three-pole, fixed mounted or draw-out type. They must be maintenance free as regards the switching element and the operating mechanism. Switching devices have to be fitted in the switchgear vessel to be independent from climate and environment. The Medium Voltage Circuit Breakers shall be designed to withstand 10,000 mechanical operating cycles respectively and 50 breaking operations at rated short circuit breaking current.

The control power for breaker closing, tripping and spring charging shall be DC 110 V. All control circuits of each Circuit Breaker shall be separately protected by means of MCB’s. The close and trip circuits shall be separately protected.

The Medium Voltage Circuit Breakers shall be provided with a minimum of two (2) Normally Open (NO) and two (2) Normally Closed (NC) spare auxiliary contacts, and wired up-to an accessible terminal block for external connections. If spare auxiliary contacts are not available, an auxiliary relay shall be used to multiply the available spare auxiliary contacts.

The tripping supply shall be monitored at the tripping coil of each breaker and a common alarm relay shall be operated if the tripping supply is unavailable.

Motor wound operating mechanisms shall be automatically recharged immediately following a closing duty. In addition to motorised spring charging, the circuit breakers shall be provided with manual spring charging facilities.

All The Medium Voltage Circuit Breakers shall have electrical / mechanical tripping facilities and the mechanical tripping button shall be accessible without opening the switchboard cover.

The Switchgear Interrupting Medium shall be SF6 or vacuum.


1.2.03 Protection and control system

General

The term "protection and control system" designates all the elements included: current and voltage sensors, relays, automation devices, trip units, associated auxiliaries, etc.

The functional units shall be equipped with integrated digital protection and control units, which include the protection, automation, measurement, counting and communication functions.

Since the Protection and Control unit is integrated as close as possible to the switchgear, it must meet the severest environmental withstand requirements, in particular IEC standards:

255-4 Impulse withstand 5 kV

255-22-1 1 MHz wave Class III

255-22-4 Fast transients Class IV

255-22-3 Electromagnetic radiation 20 V/m minimum

The operating temperature shall be up to + 45° C.

The Protection and Control units shall be operational by auxiliary power supply voltage: 110 V DC, and current sensors: 1 A - CT, and voltage sensors: 110 V - VT.

The manufacturer’s plant of the Protection Units shall be ISO 9001 certified.

The logic input shall have the same voltage rating as the auxiliary power supply and shall comply with the standards (IEC 11-32) relative to PLC’s and the current shall be at least 6 mA

Each Protection and Control Unit shall contain all the necessary specified protections.

Each protection device shall have wide setting ranges, in particular for current protections, providing a choice of curve types (direct time) DT, (IDMT) SIT, VIT, EIT, UIT and time delays from instantaneous (50 ms) to 500 s as a minimum.

Setting shall be performed by the direct input of primary current values.

Detection fault pick-up may reach 100 mA primary current.

The unit shall allow for the use of upstream and downstream logical discrimination, this applying to protection plans using IDMT times as well.

Protection tripping shall be indicated on the front of the device by a signal lamp and a message indicating the cause of the fault..

Incoming/Outgoing Feeder Protection

All functional units, which are protecting Incoming/Outgoing feeders shall be equipped with protection relays be able to perform the following protection functions:

Overcurrent


Earth fault

Remnant Under Voltage

Over/Under VoltageOver /Under Frequency

Distribution Transformer Protection

All functional units, which are protecting power transformers shall be equipped with protection relays be able to perform the following protection functions:

Thermal Overload

Overcurrent

Earth fault

Neutral Voltage Displacement

Transformer Differential

Measurement

Each Protection and Control unit shall include the measurements needed for operation and commissioning, i.e.:

Phase current measurement

Maximum phase current demand

Measurement of fault current interrupted in each phase

Additional measurements such as residual current

Measurement accuracy shall be 1 % (according to IEC 255-4).

The unit shall include voltage, frequency and energy measurements.

For power and energy data, the unit shall measure real and reactive values and take into consideration the direction of energy flow (incoming, outgoing)

Operation

The Protection and Control unit shall include display unit that indicates:

Measurement values

Operating messages in English

Maintenance messages

Circuit breaker open or closed position, displayed on the front of the device by two signal lamps

It shall be possible to make the settings and perform parameter setting via a portable terminal downloaded from Supervisory Control and Data Acquisition System Master Terminal Station.

Control and Monitoring


The Protection and Control unit shall include the input resources and logic outputs required for control of the circuit breaker

Open and close control, whatever the type of shunt trip or undervoltage release coil control

Earthing switch closed position

Lockout of making in the presence of a fault

Monitoring of the circuit-breaker operating mechanism and trip circuit (power supply, wiring and coil)

Detection of unit connected and plugged in connectors

Operation counter, fault trip counter

SF6 pressure

Cumulative total of kA interrupted

Storage of information (even during auxiliary power supply outages)

Communication

The Protection and Control unit shall be fitted with a communication interface of the MODBUS type, RS-232/RS-422/RS-485 type, 1200 – 38400-baud speed.

The unit shall provide time tagging of events within ms, with an adapted input available for an external clock synchronisation contact

Operating Dependability

The Protection and Control Unit shall include:

An internal function self-monitoring mechanism, which activates two fail-safe watchdog changeover contacts.

An automatic device for switching to the fail-safe position, with disabling of output controls when an internal failure is detected.

The indications shall be on the front of the device by signal lamps and messages indicating self-test status.

Commissioning

The Protection and Control unit shall be delivered ready to use. Only settings and parameter setting specific to the installation will need to be performed on site.

However, the unit shall include capacity for customisation and adaptation:

Extension of the number of logic inputs and outputs: to 20 inputs and 10 outputs

Modification of the control logic program shall be available on the Engineer request

Maintenance

After a spare hardware base has been set up, the proposed system shall enable restarting without any setting or the use of special equipment.


The parameter and setting values shall be saved on a movable storage medium, which is part of the unit

References

The proposed Protection and Control unit supplier shall have a large number of international references with well-known industrialists and utilities.

The list of references shall be enclosed with the proposal.

Service

The Contractor shall carry out network co-ordination studies on the Engineer request (including settings’ sheets) according to the best terms possible.

After installation, the manufacturer’s personnel shall provide all necessary services. The manufacturer shall have a competent organisation and the equipment necessary for making quick diagnoses locally.

The list of maintenance service outlets shall be enclosed with the technical proposal.

1.2.04 Power monitoring and analysis system

The term "Power monitoring and analysis system" designates all the elements included in:

The monitoring and analysis system - sensors, measuring and counting devices, monitoring and diagnosis devices

The communication interface for integration in a remote monitoring and control system

Monitoring and Analysis

The functional units shall be equipped with integrated measurement, counting, monitoring and diagnosis digital Power Analysers according to the following technical requirements:

Hardware Features

CPU - microcontroller with 20 MHz oscilator

BUS width - 8 bit data bus

ROM - EPROM 64 Kb

MAIN RAM with battery backup

REAL TIME CLOCK - embedded into RAM

EXTENDED NON-VOLATILE RAM with battery backup

Minimum 8 multiplexed ANALOGUE INPUTS with maximum 10ms sample / conversion time

Minimum 8 programmable opto-isolated DIGITAL INPUTS

Software Requirements

HIGH-SPEED SETPOINT CONTROL SYSTEM


SIGNAL PROCESSING SOFTWARE

Measured Parameters

Voltage per phase (L-N/L-L)

Current per phase

Auxiliary current (earth leakage)

Digital inputs

Frequency

Calculated Parameters

True RMS phase-to-neutral voltage (per phase)

True RMS line-to-line voltage (per phase)

Unbalanced current

Earth leakage

Active power (per phase and total)

Reactive power (per phase and total)

Apparent power (per phase and total)

Power maximum demand

Accumulated demand (per phase)

Ampere demand (per phase)

Active energy (imp, exp, net, tot)

Reactive energy (imp, exp, net, tot)

Apparent energy (imp, exp, net, tot)

Power factor (per phase and average)

Voltage and current harmonics per phase (up to 31 harmonic)

Total harmonics distortion (THD) per phase (voltage and current)

Displayed Parameters

All measured and calculated parameters and status inputs.

Alarm/Events Set Points

Over/under current

Over/under voltage

Over/under power factor


Over/under active power

Over/under reactive power

Over/under apparent power

Over accumulated power demand

Over unbalanced current

Over/under frequency

Over THD

Over/under date

Over/under time

Over/under pulse counter (1-8)

Status inputs (1-8)

Relay status (1-8)

User/manual control (1-8)

Relay Operation

Alarm/event set-point controlled

kWh, kVArh, kVAh and maximum demand interval pulse out

Manual controlled via communication channel

Status / Input

Alarm/event conditions

External demand interval synchronisation

Programming multiplexed analogue output

Analogue Output Operation

Current output range 4-20 mA per order

Any measured quantity may be assigned to analogue output

User-configurable zero offset and full scale factors

Set Up

Downloaded from PC or done manually from keyboard

Full software support

Parameter Access Designation

K - Keypad access


C - Communication access

Set Up Access (K)

Password option (ON/OFF)

Password check

Redefine password

Time Clock Setting (K/C)

Year, month, day, hour, minute

Resetting seconds

Digital Inputs Allocation (K/C)

For analogue output selector when multiplexed analogue output is used (1-4)

For monitoring external dry contacts (1-8)

For external synchronisation source to reset power demand interval (1)

For triggering alarm/event conditions (1-8)

Analogue Output (K/C)

Non-multiplexed/ multiplexed

For multiplexed output: the number of digital inputs used as selector for programming multiplexed analogue output and the measured parameters associated with the analogue output selector’s keys

For non-multiplexed output: he measured parameters assigned to the analogue output

For any selected analogue parameter: low scale corresponding to a zero-scale analogue current - 4 mA and high scale corresponding to the full-scale analogue current - 20 mA.

Relay Control (K/C)

Alarm/event set-point controlled

kWh, kVArh, or kVAh pulse output

Maximum demand interval pulse output

Pulse duration for pulse mode allocation (100-1000 ms)

Alarm/Events Set-points (K/C)

Set Point Definition

Condition input group (real-time/average analogue value, pulse counter, status input, relay status, user event)

Condition reference


Time delay to operate (0.1-999.0 s)

Time delay to release (0.01-999.0 s)

Action 1st reference

Action 2nd reference

Condition Definition

Analogue value:

Analogue parameter

Compare

Operate limit

Release limit

Pulse counter:

Counter number

Compare

Operate limit

Release limit

Status input:

Status input number (1-8)

Operate status (ON/OFF)

Relay status:

Relay number (1-8)


User events / manual control:

User event flag (1-8)


Action Definition

Relay control

Set/reset user event

Increment/decrement/clear counter

Reset/clear: energy registers, maximum demand registers

Reset Control (K/C)


Reset functions enabled/disabled (ON/OFF)

Reset energy registers

Reset maximum demand registers

Communications Parameters (K)

Communications protocol (ASCII/MODBUS)

Interface (232/422/485)

Baud rate and data format (38400 baud minimum, 8 bit, no/even parity)-

Handshakes (OFF/RTS-CTS)

Instrument address (1 - 247)

Data Scale Factors

Voltage high scale (+)

Current high scale(+)

Power low scale(+/-)

Power high scale (+)

Sampling

Instrument shall be able to sample 128 samples per cycle. No degrading in accuracy shall happen up to 65 Hz.

Sampling rate shall be synchronised exactly to the fundamental frequency so that the harmonics measurements will not be falsified by adjacent frequencies.

Averaging

Number of buffer entries used for average shall be 8/16/32 entries.

Wiring Configurations

Four wiring configurations shall apply:

Three-wire system configuration direct connection

Four-wire system configuration direct connection

Four-wire system configuration, wiring via PT Y-Y connection

Three-wire system configuration, wiring via PT with open delta connection

Waveform Capture

Waveform capture shall let the user trigger via communications and upload to the PC 4 cycles x 2 inputs of voltage and current waveforms on any phase, sampled synchronously at a rate of 128 samples per cycle, allowing detailed spectrum and waveform analysis.

Alarm / Event Set Points


Alarm/event set points shall be defined for all parameters to trigger up to 4 relay or activate any logging function. Set points shall be set by keyboard or via communications.

For any set point, it shall be possible to define:

Event condition

Up to 2 set-point actions

Time delays to operate/release set-point (histeresis)

Time resolution (0.1 s/1 s)

For any set-point, it shall be possible to define two delay values: one to activate a set-point when conditions are true, and the second - to deactivate (in the range from 0.1 to 999.0 s at 100 ms resolution, or from 1 to 9999 s at 1 s resolution).

Conditions

Over/under the limit of a measured analogue value

Over/under date or time

Over/under pulse counter

Status input ON/OFF

Relay status ON/OFF

User event/manual control ON/OFF

Eight user controlled global events shall be possible to set/reset by a set point or manually via communications to trigger any set-point.

For over/under the limit condition, it shall be possible to specify the ON and OFF thresholds (limits) to activate the condition, and the value evaluation base (real-time one-cycle calculation average value).

Alarm/Event Actions

For any set point violation, it shall be possible to assign the following actions:

Relay control

Pulse counter control

User event control

Reset cumulative registers (selectively or all)

Communication Interface and Features

Digital Power System Analysers shall be capable to interface with the RTU’s by acceptable protocols:

RS-232/RS-422/RS-485 communication

Baud rate from 1200 up to 38400


RTS/CTS, MODBUS protocols

Configuration Information

Set-point system

Data logging

Status input

Instrument status

Interposing Relays

Ratings

4 relays rated at 5A 250 VAC, 30 VDC, 3 contacts SPDT. All relays shall be de-energised.

Operations

Any relay shall be configured to indicate:

Set-point violation

Energy pulsing

Maximum demand interval pulsing

Tariff time interval pulsing

Alarms/Events Relays Set Points

Each of the programmable set points shall be allocated to any of the 4 relays.

Energy Pulsing

kWh, kVArh, and kVAh pulsing shall be available for interface with PLC’s or other electronic devices. It is available on any one of the relays.

Pulsing options shall be as follows: 1 pulse per 1 unit to 200 units

Contacts shall be closed for approx. 100 ms each pulse by default. Pulse width shall be changeable by programming.

Maximum Demand Interval Pulsing

Any relay shall be able to be configured to output a time pulse indicating the beginning of a maximum demand time interval. The timing pulse should be synchronised with the beginning of an hour.

Analogue Output

1 Channel 4 - 20 mA programmable non-multiplexed/multiplexed.

High CMV isolation: 1500 V RMS

Low offset temperature: ± 300 nA/°C

Non-linearity: ± 0.02%


It shall be possible to define the scaling of the analogue output through communications or through keyboard. Output range shall have default value set in factory. It shall be possible to determine the zero offsets and the conversion coefficients.

Start -up

Upon power up, the instrument shall start with self-test. Start-up procedure shall include:

Memory read/write test

Configuration test

1.2.05 Current transformers

The Current Transformers for protection and measurements shall be based of the conventional type toroidal Current Transformers of the single or multi-ratio type, mounted inside the medium-voltage enclosure with grounded cores.

The rated secondary current of toroidal Current Transformers shall be 1 A.

The toroidal Current Transformers shall have secondary terminals outside the medium-voltage enclosure, mounted in suitable, accessible terminal boxes. All secondary leads of all Current Transformers must be wired to shorting-type terminals on the terminal strip in the local control cubicle of each bay.

The Current Transformers shall be 0.5 Class or better.

1.2.06 Voltage transformers

The Voltage Transformers for protection and measurements shall be of RC-divider type. They shall be mounted directly on the medium-voltage enclosure with plug-in contacts to allow easy removal.

The secondary terminals of the Voltage Transformers shall be located in easy accessible, grounded terminal boxes on the voltage transformer itself. The secondary connections must be wired to a terminal strip in the local control cabinet.

The Voltage Transformers shall be 0.5 Class or better

1.2.07 Lightning arresters

The Contractor shall perform simulation with the actual plant data to give accurate determination of the over-voltages and to design number and location of lightning arresters.

1.2.08 Auxiliary contacts

The switchgear shall be equipped with auxiliary indication contacts connected to terminals in the factory.

The terminal blocks, which received the available auxiliary contacts, shall be located in the low voltage compartment.

1.2.09 Low voltage auxiliaries

The protection and control system shall also be equipped with:


Test units for the injection of current or voltage into the transformer secondary circuits, installed on the front of the low voltage compartment:

1 unit for voltage

1 unit for measurement current circuits

1 unit for protection current circuits

1 unit for the zero current circuit

Low voltage protection circuit breakers, located in the low voltage compartment. Fuse protections are not acceptable.

A "local-remote" selector switch shall be installed for integration in a remote monitoring and control system.

The low voltage auxiliaries shall comply with the standards IEC 298 section 5-4 and IEC 694, article 5, section 5.4.

The low voltage cables shall be of the self-extinguishing, 1000 V insulation class. Both ends shall be identified to facilitate checking during maintenance operations.

For the current circuits, the cable cross-section shall 2.5 mm², and 1.5 mm² for the other circuits.

1.2.10 Enclosure

Steel enclosures: minimum 2 mm thick electro-galvanized sheet steel. It shall be painted to provide protection against corrosion. The epoxy based paint shall have a thickness at least 50 microns and shall be applied at both side of all sheet metal. The colour shall correspond to the RAL colour range proposed.eel enclosures: minimum 2 mm thick electro-galvanized sheet steel. It shall be painted to provide protection against corrosion. The epoxy based paint shall have a thickness at least 50 microns and shall be applied at both side of all sheet metal. The colour shall correspond to the RAL colour range proposed.

1.2.11 Assembly

The Medium Voltage Switchboards shall be of the modular design for free combination and extension.

They shall be rigid, ventilated, insect-screened enclosures consisting of panels, doors, or both, giving the designated enclosure, separation and degree of protection.

The Medium Voltage Switchboards shall be single tier, floor mounted, free standing suitable for tropical indoor application in accordance to the requisition specification. The Switchboard shall be designed for ease of maintenance and operation with the height of equipment requiring regular operation and testing being kept to a minimum.

The construction of the Medium Voltage Switchboards shall allow for future extensions at either end. Certified lifting lugs shall be provided in each shipping sections of the switchboard.

All cubicles shall be manufactured from electro-galvanised steel sheets with a minimum thickness of 2.0 mm. on a framework of folded sheet steel or structural sections. The


Switchboard construction shall be such that no distortion occurs when it is being lifted by hoist or moved into position on rollers.

The components used shall be of proven design with high service reliability and maintenance free long life features. Where relevant, components shall have flame retardant properties.

Gland plates and enclosure panels shall be provided with captive nuts or screws.

1.2.12 Earthing

An earthing bar of hard drawn, high conductivity copper shall be installed the full length of the switchboard in the bottom compartment. All metallic, non-current carrying parts of the switchboards shall be effectively and securely connected to this earthing bar. All gland plates shall be earthed to the earth bar.

Earthing bolts, lugs, nuts and spring washers shall be provided at each end of the bar suitable for the connection of 1x240 mm2 earthing cables to the external main earthing grid.

All doors and covers of the switchboards shall be effectively earthed using flexible connections.

An integrally mounted three phase earthing switch, capable of making and carrying the full perspective short circuit current and suitable for local manual operation shall be provided on the cable side of all Medium Voltage switching devices. Earthing facilities for the earthing of the busbar system of each section shall also be provided.

Earth Continuity

The earthing bars of each of the cubicles making up the switchboard shall be interconnected by a set of busbars which shall be connectable outside the switchboard and extend over its full width.

The cross-section of the busbars shall be determined so as to withstand the rated short-circuit current of the switchgear in accordance with IEC 60298 recommendations.

The earthing bar shall be designed for connection to the main earthing bar of the substation without dismantling any of the bars.

Effectively bond equipment and assembly cabinet metal frame to the protective earth conductor. Strip painted surfaces and coat with corrosion resistant material immediately before bolting to the earth bar. Provide serrated washers under bolt heads and nuts at painted, structural metal-to-metal joints.

Earthing of the Power Circuit

Cable earthing shall be carried out by an earthing switch with short-circuit making capacity, in accordance with IEC 60129 recommendations. It shall be possible to operate the earthing switch when the switch or disconnector is open.

A padlocking system shall be provided to lock the earthing switch in either open or closed position. The position of the earthing switch shall be clearly visible from the front of the cubicle.

Mechanical interlocking systems shall be provided to prevent incorrect operations such as the closing of the earthing switch with the switch or disconnector in closed position.


The use of keyed or electric locks to actuate the above mentioned interlocking system shall not be accepted.

1.2.13 Cable entries

Provide cable entry facilities within incoming and outgoing sections. Provide sufficient clear space for cables not to be stressed or impose on there bending radius. Please specify the cable entry trench depth.

The gland plates shall be fitted with gaskets to maintain the degree of protection, materials: pre-drilled 1.6 mm thick electro-galvanised steel.

1.2.14 Cable ducting

The Contractor shall design and construct cable ducting facilities within the premises of Medium Voltage Switchboard Chamber for incoming and outgoing cables. Provide sufficient clear space for cables not to be stressed or impose on there bending radius.

1.2.15 Cover and gland plates

Gland plates: Provide removable gland plates fitted with gaskets to maintain the degree of protection made from 1.6 mm thick electrically galvanised steel.

1.2.16 Doors and covers

Space adjacent doors to allow both to open to 90o at the same time. The single right angle return shall be implemented on all sides and fit suitable resilient sealing rubber to provide the degree of protection and prevent damage to paintwork.

The all doors shall be fitted with corrosion-resistant lever-type handles, operating a latching system with latching bar and guides strong enough to withstand explosive force resulting from fault conditions within the assembly.

Earth continuity shall be maintain to door in all positions.

The covers shall be fixed to frames with at least 4 fixings. Provide corrosion-resistant acorn nuts if the cover exceeds 600 mm in width. Rest cover edges on the cubicle body.

1.2.17 Busbars

The main circuit supply busbars within assemblies, extending from incoming supply terminals to the line side of protective equipment for outgoing functional units and for future functional units.

The busbars shall be installed in segregated enclosed compartments. No wiring equipment or devices shall be installed in the busbars compartments. The busbars shall be of hard drawn high conductivity bars made of tough pitched tinned copper alloy using electrolytic copper and have the same current rating throughout the length of the entire Switchboard.

A fully fault rated earth bus shall be provided in the switchboard and the size shall be indicated in the offer.

Sufficient supports made from non-hygroscopic insulation material capable of holding busbars at 105oC.to shall withstand thermal and magnetic stresses under maximum prospective fault currents.


For active conductors calculation it shall be taken into account Take into account thermal stresses due to short circuit current, assuming magnetic material enclosures located indoors in well-ventilated rooms and 90oC final temperature.

The size of protective earth conductors shall be at least 50% of the rated short-circuit withstand current for 100% of the clearance time.

1.2.18 Interlocking and padlocking

In general the following minimum padlocking facilities shall be provided:

Panel door

Local trip/close switches (electrical / mechanical)

Earthing switch in closed position

The Switchboard manufacturer shall recommend and provide the details of the interlocking required for busbar earthing.

1.2.19 Fastenings

ISO metric nuts and bolts in accordance with the requirements of ISO1111 and ISO1112 shall be used in the construction of the Switchboard. All fastening shall be corrosion resistant.

Cover bolts shall be retained in place when undone.

1.2.20 DC power supply

All DC power supply units necessary for the complete, satisfactory and independent operation of all the Medium Voltage Switchgears are to be included in this Contract. DC supply voltage for the Medium Voltage Switchgear shall be 110 volt. Capacities of the DC supply system shall be determined by the Contractor to satisfy the Functional Units correct performance.

Batteries

Batteries to be nickel/cadmium type. Dual rate (trickle/booster) charger, ammeter, voltmeter, indicating lamps, fuses must also be provided. All components of the DC supply units shall be housed in a metalclad enclosure with hinged door floor or wall mounted.

A battery test switch and all necessary test components shall be provided to test the discharging capacity of the DC supply units.

Battery Charger

The tripping battery shall be of sufficient capacity to supply the tripping current of three units simultaneously and housed in a self contained free standing ventilated steel sheet cubicle. Together with the batteries, there shall be installed with the automatic charging equipment, fuses for outgoing circuits, ammeter, mains or indication lamp, non locking load test switch, voltmeter with terminal voltage clearly marked in red on scale inclusive of engraved instruction label for manner and duration of test.

1.2.21 Operation

In order to make the Medium Voltage Switchboard simple and safe to use, the following construction requirements must be met:


Operating Mechanisms

All operating mechanisms and access points shall be on the front of the functional units, in particular, cable and busbar connections must be accessible via the front.

Instruction Guide

The operating procedures for the most current operations must be described on the front of each functional unit.

This shall be described exclusively in the form of explicit symbols and colour codes.

1.2.22 Main offer

The Main Offer shall comprise a quotation including:

The technical proposal to meet the Specification

Proposed variances with respect to the Specification

This document shall be accompanied by at least the following:

Technical documents presenting the equipment

Single-line diagrams of all the switchboards

Low voltage functional diagrams

Dimensional and layout drawings, with mounting and cable running

An accurate representation of the front view of the equipment

The list of test certificates related to the requested performances

The services associated with equipment supply

Any options, with prices and impact on equipment availability time

Operating and servicing documents

The list of spare parts with prices, indicating the average delivery lead times

Warranty terms

Before an order is placed, the supplier will be requested to supply the complete wiring diagrams, as well as the engineering and installation documents.

1.2.23 Labels

Label with essential markings shall include:

Manufacturer’s name

Switchboard type designation

Purchaser order number

Switchboard title and tag number


Year of manufacture

Service voltage, rated frequency

Rated current of the busbar system

Rated voltage of the auxiliary circuits

Rated peak and short time withstand current and withstand time

Degree of protection

Designation labels: For other than main assemblies, provide designation label stating source of electrical supply. Identify separate sections of enclosures

1.3 MANUFACTURING

1.3.01 Manufacturer

The Medium Voltage Switchboards and their components shall be manufactured in the factory(ies) certified with ISO 9001 certificate with at least 10 years experience in the specified equipment production

1.3.02 Inspections

The equipment may be inspected during manufacturing in any of the plants, which are involved in the related manufacturing. The Contractor shall make provision in his rates to cover the Engineer expenses for such inspection.

The equipment shall be delivered with all the documents required for installation, testing, commissioning, operation and servicing-maintenance.

The Contractor shall notify the Engineer so that inspections may be conducted at the following stages:

Fabrication and painting completed.

Factory assembly completed, with busbars exposed and functional units assembled.

Assembly ready for routine testing and dispatch.

Assembly installed and connected.

Acceptance and handover.

1.4 TEST

1.4.01 Type test

The Contractor shall submit for the Engineer’s approval with the proposed manufacturer Medium Voltage Switchboards Type Test certificates from independence laboratory (KEMA or equivalent).

The Contractor shall present the following type testing certificates:

Impulse dielectric withstand test

Dielectric withstand at power frequency test


Overheating test

Admissible short time current withstand test

Mechanical operation test

Degree of protection check

Electromagnetic compatibility check (EMC test)

Switchgear device breaking capacity checks

Switchgear device making capacity check

1.4.02 Routine testing

All equipment covered by this specification shall be subject to the Engineer’s inspection at the manufacturer’s works. The manufacturer shall notify the Engineer fourteen (14) days in advance when the tests are to be performed. Carry out the following tests:

Assemblies: Electrical and mechanical routine function tests at the factory using externally connected simulated circuits and equipment.

Dielectric testing:

Functional testing: Operate mechanical devices, relays, protection, interlocking and alarm equipment.

Primary and secondary current injection test

Insulation resistance test

AC voltage/Power frequency one minute test

Impulse voltage test

Wiring continuity test

Functional test of all components

All test reports/certificates shall be submitted to Engineer within fourteen (14) days of the completion of such tests.

Test reports and certificates shall be approved by the Engineer prior to the equipment leaving the factory.

If the test results show that any equipment of the purchase order is not met, Supplier shall make necessary correction to the satisfaction of the Engineer before acceptance is made.

1.5 INSTALLATION

Installation of the Medium Voltage Switchboards shall be carried out according to the manufacturer’s recommendations and relevant drawings and in conformity with IEE regulations and applicable IEC standards.

The Switchgear manufacturer shall be capable of providing all the services necessary, from training of personnel to installation and full commissioning on site if required by the Engineer.


1.5.01 Transportation

Each functional unit shall be set on and screwed onto a wooden floor.

The units shall be individually protected against rain and dust by polyethylene wrapping, in which desiccant bags are placed.

Wooden straps shall be used to protect against impact.

1.5.02 Handling and storage

The wooden floor onto which each functional unit is screwed should allow for handling by a forklift.

The switchgear should be capable of being stored for as long as necessary in the following conditions:

Splashing water, wind, sand and all direct chemical pollution

Humidity in compliance with that defined for normal operating conditions

1.6 TESTING AND COMMISSIONING

Field testing and commissioning of the Medium Voltage Switchboards shall be carried out by the code of InterNational Electrical Testing Association (NETA).

Only qualified personnel shall test and commission the Medium Voltage Switchboards.

1.6.01 Site testing

In order to reduce commissioning time, the equipment proposed shall be designed so that the commissioning of each functional unit does not require an additional individual testing of each protection and measurement function.

Testing shall be limited to:

Checking of the parameter settings by direct reading

Checking of the connections to the current and voltage sensors by secondary injection

Measurement of residual current and voltage for configurations which use those values

Checking of logical input/output wiring

Switchgear device operation by push-button

Pilot wire connection test

No configurations, which require other test procedures, will be accepted.

1.6.02 Commissioning

The only settings required during the commissioning of the Medium Voltage Switchboards shall be parameter settings of the protections and the alarms on the protection and control unit.

Sel1 Hv Switchboards

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