Chiller PQ Issues - EPRImydocs.epri.com/.../E232227_Chiller_PQ_Issues.pdf · · 2009-12-18Chiller...

1

Chiller PQ Issues

Mark Stephens, PESenior Project ManagerIndustrial Studies Electric Power Research Institute 942 Corridor Park Blvd Knoxville, Tennessee 37932 Phone 865.218.8022

[email protected]

mailto:[email protected]

2 Copyright © 2009 Electric Power Research Institute, Inc. All rights reserved. PQIG 2009

HVAC and Chiller Basics: Commercial Office Building Example

3. Refrigeration Loop

2. Chilled Water Loop

1. Airsideloop

4. Heat RejectionLoop

5. Building AutomationSystem (Optional)


HVAC and Chiller Basics: Industrial Process Cooling Water Example

BAS(Optional)

HeatExchanger

HeatExchanger

Evap

o rat

orEv

apo r

ator

SecondaryPCW

Loop toProcessLoads

FromProcessLoads

Capacity ControlValve

(2 or 3 Way)

ChilledWater

Pump(s)

Con

dens

e rC

onde

nse r

CompressorCompressor

ExpansionValve

ExpansionValve

Cooling Tower Pump(s)

Cooling Tower Pump(s)

3WayModulating

Valve

3WayModulating

Valve

3WayModulating

Valve

CoolingTower

CoolingTower

Chiller System

PrimaryChilled WaterLoop

Refrigeration Loop

HeatRejection

Loop

95°

85°85°

95°120°

100°38°

50°80°

55°55°

80°

BTU Flow


Susceptibility Concerns for Chiller Systems

• Voltage Sag Induced Shutdowns:– Weak Control Relay in Chiller Control Cabinet (pilot relay)– Chiller controls or micro settings do not allow for voltage sag

induced deviations– Interlock with Chilled Water Supply (CWS) Flow Switch or with

Chilled Water Pump contactors– Shutdown due to Over-current– ASD Shutdown due to DC Bus Trip Level

• Shutdown due to Voltage/Current Unbalance– Chiller controls or micro settings too tight for typical unbalance

conditions– Phase-Monitoring Relay in MCC or control panel


Survey/Case Study Breakdown

46%

40%

7% 7%Voltage Sag/MomentaryInterruptionVoltage Unbalance

Harmonics

Flicker

Based on Survey/Case Study Responses


What happens to Customer’s HVAC/Chiller System during a Voltage Sag?

Any one or more of these equipment may tripdepending on the sensitivity of the equipment/control:

• Chiller Control Panel

• Chiller Starter

• Chilled Water Supply (CWS) Pump

• Condenser Cooling Water Pump

• Air Handling Unit Motor Controls


Trane Centravac Chiller

Evaporator

Condenser

Chiller ControlPanel

CompressorCompressorMotor StarterPanel


McQuay Chiller


York Chillers

OM SeriesTurbomaster

MaxESeries with SoftStart

MillenniumYK Series


York Chiller With Solid State Starter


York Chiller With Electro Mechanical Starter


York Chiller With ASD

13

Control Panel PQ Issues



• AC Input Board – Inputs subject to misinterpretation/device chatter from Voltage Sag Events can lead to shutdown

• Relay Output Board – Control of vane and orifice valves, chiller compressor starter/pilot relay

Control Voltage 120Vac 50/60Hz fromControl Power Transformer (2-3kVA Typical)

AC Input Board

Stop Compressor

Start Compressor

CWS Flow Switch

CWP Running

Relay Output Board

Open

CloseVaneMotor

Open

Close

OrificeValveMotor

Run Oil Pump OilPumpStarter

Run Compressor* PilotRelay

Multiple Solenoid Valves(oil return, liquid line, vent line, etc.)

L1 N

Compressor Running

Warm Oil OilHeaterRelay

Oil Heater Relay Contact

Oil Pump Heater

5Amp

20Amp

*Note: Some Manufacturers utilize a data Link toseperate microprocessor based Starter Panel wherePilot Relay and starter contactors are located. Thispanel also contains another control powertransformer.



• Linear/Switch Mode Power Supply for Instrumentation

• Microprocessor for control decisions

• DC Input board for instrumentation measurements (Pressure/Temp)

• Motor Protection Board: Measures Phase Current and Voltage

Compressor Current Ph. B

Power Supply Board

Control Voltage 120Vac50/60Hz (continued)

L1 NVdc Return

Microprocessor

DC Input Board

Compressor Current Ph. A

Compressor Current Ph. C

CT1

CT2

CT3

PT

TT

Various PressureTransmitters

Various TemperatureTransmitters

Compressor Motor ProtectionMonitoring Board/Relay

Compressor Voltage Ph. B

Compressor Voltage Ph. A

Compressor Voltage Ph. C

Va

Vb

Vc

Interlock withMicroprocessor


Control Power Schemes

Notes:1.An external control power transformer

may be used to feed both the microprocessor panel and the compressor starter panel. In this case, applying voltage conditioning from this power source can lead to a must more robust chiller control system.

2.Some vendors mount the control power transformer in the starter panel. This transformer can be used to supply control voltage to the starter internal to the panel as well as for the microprocessor control panel.

3.The control signals between the two panels will either consist of hardwired control signals between the starter elements in the panels or a datalink to a separate starter microprocessor that is located in the starter panel.

CompressorMotor

Starter Panel

CompressorMotor

Starter Panelwith Control

PowerTransformer 2

MicroprocessorControl Paneland Display


External Control Power Transformer 1

ControlSignals 3

ControlSignals 3

Control PowerControl Power

Control Power

CompressorMotor

Starter Panelwith Control

PowerTransformer 2


ControlSignals 3

Control Power

PowerDistribution

Panel

Configuration "1"

Configuration "2"

Configuration "3"


Control Power Schemes Evaluated by EPRI

Micro to starter panel

Unit ConfigurationStarter Type Control Signal Reason for Susceptibility

A 2 wye-delta Datalink Motor Starter, Voltage Unbalance setting

B 2 wye-delta Hardwired Motor Starter

C 2 soft starter Datalink Contactors used in running mode

D 2 wye-delta Datalink Pilot Relay and Motor Starter

E 1/3 across line Hardwired Pilot Relay

F 1/3 soft starter Hardwired Pilot Relay


Chiller Voltage Sag Susceptibility – Unit A

SingleSingle--Phase Voltage SagsPhase Voltage Sags PhasePhase--toto--Phase Voltage SagsPhase Voltage Sags

Background Background -- Control Power Transformer Connected acrossControl Power Transformer Connected acrossPhases A and B. Tested in EPRI Lab.Phases A and B. Tested in EPRI Lab.Reason for susceptibility Reason for susceptibility –– Control Relays and Surge DeltaControl Relays and Surge DeltaAmp SettingsAmp Settings


Chiller Voltage Sag Susceptibility – Unit B

0

1020

3040

5060

7080

90

0 10 20 30 40 50 60

Cycles

%V

nom

inal

Motor Controls Trip

Motor ControlsChatter/DropoutChiller Controls Only

CBEMA/ITIC

PhasePhase--toto--Phase Voltage SagsPhase Voltage Sags

Background Background -- Control Power Transformer Connected acrossControl Power Transformer Connected acrossPhases A and B. Tested at site where unit is installed. Phases A and B. Tested at site where unit is installed. Reason for susceptibility Reason for susceptibility –– Control Relay in Control Relay in WyeWye--Delta Starter.Delta Starter.


Chiller Voltage Sag Susceptibility – Unit C


Background Background -- Control Power Transformer ConnectedControl Power Transformer Connectedphasephase--toto--phase. Chiller utilized 480Vac soft starter, tested at EPRI phase. Chiller utilized 480Vac soft starter, tested at EPRI lab.lab.Reason for susceptibility Reason for susceptibility –– Compressor Motor Contactor Chatter afterCompressor Motor Contactor Chatter afterSoft starter is out of circuit (normal running operation).Soft starter is out of circuit (normal running operation).

Voltage Sag Ridethrough Curve

0%20%40%60%80%

100%

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Duration (in seconds)

Volta

ge (%

of N

omin

al)

DUT SEMI F47


Chiller Voltage Sag Susceptibility – Unit D


Background Background -- Control Power Transformer ConnectedControl Power Transformer Connectedphasephase--toto--phase. Chiller utilized phase. Chiller utilized wyewye--delta 480Vac starter. Tested at EPRI .delta 480Vac starter. Tested at EPRI .Reason for susceptibility Reason for susceptibility –– Compressor Motor Contactor Chatter.Compressor Motor Contactor Chatter.““Momentary Power LossMomentary Power Loss”” warning shows up for Phase C sags only and results in warning shows up for Phase C sags only and results in Shutdown.The chiller Micro only monitors that phase for power loShutdown.The chiller Micro only monitors that phase for power loss.ss.““Transition Complete Input OpenTransition Complete Input Open”” message displayed on phase A and B sags whenmessage displayed on phase A and B sags whenMotor contactors and relays cause the chiller to trip.Motor contactors and relays cause the chiller to trip.

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30

Cycles

%Vn

omin

al Phase C-NPhase B-NPhase A-NSEMI F47

SingleSingle--Phase Voltage SagsPhase Voltage Sags

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30

Cycles

%Vn

omin

al

Phase A-BSEMI F47


Chiller Voltage Sag Susceptibility – Unit E

Component Voltage Sag SummaryComponent Voltage Sag Summary

Background Background –– 120Vac Test of control panel. Chiller utilized line starter. T120Vac Test of control panel. Chiller utilized line starter. Tested atested atChiller Manufacturer Lab.Chiller Manufacturer Lab.Reason for susceptibility Reason for susceptibility –– Compressor Motor Pilot Relay. Chiller required 2 minutesCompressor Motor Pilot Relay. Chiller required 2 minutesTo reset and allow a restart (typical for most chillers to allowTo reset and allow a restart (typical for most chillers to allow for the compressor tofor the compressor toSpin down).Spin down).

SingleSingle--Phase Voltage SagsPhase Voltage Sags

6965

60

00

10

20

30

40

50

60

70

80

1R Relay* CompressorStarter

Oil PumpStarter

24Vdc P/S**

%Vn

omin

al


Chiller Voltage Sag Susceptibility – Unit F

Soft Starter Susceptibility to SingleSoft Starter Susceptibility to Single--Phase SagsPhase Sags

Background Background –– 120Vac Test of control panel with solid state starter electroni120Vac Test of control panel with solid state starter electronic starter. c starter. Tested at Chiller Manufacturer Lab.Tested at Chiller Manufacturer Lab.Reason for susceptibility Reason for susceptibility –– Compressor Motor Pilot Relay. Chiller required 2 minutesCompressor Motor Pilot Relay. Chiller required 2 minutesTo reset and allow a restart (typical for most chillers to allowTo reset and allow a restart (typical for most chillers to allow for the compressor tofor the compressor toSpin down). Soft Starter electronics robust since powered by DCSpin down). Soft Starter electronics robust since powered by DC power supply.power supply.

SingleSingle--Phase Voltage Sags Phase Voltage Sags

24

Chilled Water Loop Considerations


Chilled Water LoopsPrimary and Secondary

PLC ASDs Pumps


Chilled Water LoopsTypical PLC Interface

Loop Number Description Source Voltage Note QI-191 P-191 Run

Status 120Vac Control Relay (Model # AB/700-HC24A1) CR7 coil voltage from drive control power transformer (CPT)

Signal Susceptible to voltage sags due to sensitive “ice cube” relay.

QA-191 P-191 Fault 120Vac Control Relay (Model # AB/700-HC24A1) CR6 coil voltage from drive control power transformer (CPT)


HS-191-2 P-191 Start/Stop Control RelayCR9 fed from PLC control power

PLC control power on UPS. Signal not expected to be susceptible to voltage sags.

HY-191 P-191 in Auto 120Vac control relay CR8 fed from drive CPT.


HIC-191 Pump P-191 Pump Speed Control Signal

4-20ma Signal fed through power supply in PLC cabinet.

PLC control power on UPS. Signal not expected to be susceptible to voltage sags.

PLC ASDs


Example PCW Pump PLC-Drive Hardwired Interface

Fab Quadrant A/B PCW Pumps 610,611,612

Two-Relay PLC Interface Scheme and

Control Power Transformer

(Estimated at 0.25kVA)

Fab Quadrant C/D PCW Pumps 614,615,616 Four-Relay PLC Interface

Scheme and Control Power Transformer

(0.2 kVA)

Fab Quadrant E PCW Pumps 617,618,619

Four-Relay PLC Interface Scheme and

Control Power Transformer (0.38 kVA)


A Satisfactory Response for One Application May Not Be for Another

• For HVAC application an automatic restart or a manual restart after time delay may be the best option - in that case the tripping of the chiller unit does not have significant impact oncustomer.

• However, for process chilled water application, the loss of the chiller or the CWP may have significant financial impact.

29

Chiller Voltage Unbalance Issues


Voltage Unbalance and Chillers

• Shutdown occurs when the chiller's current sensing relay/micro processor detects an imbalance or over current condition in excess of the preset limits.

• Chiller shutdown is influenced by the single phase loading conditions internal and external to the building electrical system.

• The American National Standards Institute (ANSI) std. C84.1-1989 recommends that voltage imbalance on power lines should not exceed 3%.

• Some factory preset imbalance protection limits cause chillers to shutdown or operate at reduced capacity when the chiller is experiencing an amperage imbalance. Example Chiller setpoint range 5% to 40%.

Rule of Thumb:1% Voltage Unbalance

Leads to 6 to 10%Current Unbalance

%Voltage %Current ImbalanceUnbalance Min Max

0.25% 1.50% 2.50%0.50% 3.00% 5.00%0.75% 4.50% 7.50%1.00% 6.00% 10.00%1.25% 7.50% 12.50%1.50% 9.00% 15.00%1.75% 10.50% 17.50%2.00% 12.00% 20.00%2.25% 13.50% 22.50%2.50% 15.00% 25.00%2.75% 16.50% 27.50%3.00% 18.00% 30.00%


Voltage Unbalance And HP Derating

• If voltage imbalance present, may have to derate chiller cooling capacity (maximum amp) to protect motor.

• For Motors with Service Factors of 1.5, allowable %Current Imbalance to 30%.

Application Note 12 – Matching Utilization Voltage to Motor Nameplate


Motor Service Factor

Motor Service Factor (SF) is a factor that when multiplied by Motor Service Factor (SF) is a factor that when multiplied by horsepower, gives us the allowable horsepower loading, which mayhorsepower, gives us the allowable horsepower loading, which maybe carried under the conditions specified for the service factorbe carried under the conditions specified for the service factor at at rated voltage and frequency. This is practical as it gives you srated voltage and frequency. This is practical as it gives you some ome 'fudge' in estimating horsepower needs and actual running 'fudge' in estimating horsepower needs and actual running horsepower requirements. It also allows for cooler winding horsepower requirements. It also allows for cooler winding temperatures at rated load, protects against intermittent heat rtemperatures at rated load, protects against intermittent heat rises, ises, and helps to offset low or unbalanced line voltages.and helps to offset low or unbalanced line voltages.

Click Here for More on Motor Nameplate Data


Chiller Voltage Unbalance and Current Imbalance Parameters


Recommended Chiller Micro/Motor Protection Settings

Parameter Function Recommended Setting for best

PQ performance

Note

Voltage Unbalance

Measure of allowable phase Voltage

Unbalance

>3% From ANSI C84.1, 98% percent of the electric

supply systems surveyed are within the 0-3.0 percent

voltage unbalance range

Voltage UnbalanceTime (sec)

Delay Time in which Unbalanced Voltage

Must be Present Before Chiller Trips

5 Second Minimum

Instantaneous Settings not recommended

Current Imbalance

Measure of allowable phase current

Imbalance

20%-30% For motors with Service Factors of 1.15 or greater

Current Imbalance Time (Sec)

Delay Time in which Imbalanced Current

Must be Present Before Chiller Trips

5 seconds Minimum

Instantaneous Settings not recommended


Recommended Chiller Micro/Motor Protection Settings

Parameter Function Recommended Setting for best PQ performance

Note

Auto Restart Option

Restarts chiller after shutdown

Enable Always consider auto start features or auto start up of

an adjacent chiller upon the fault of the unit that is

running.Single Cycle

DropoutDetects Loss of Power

for a Single CycleDisable Parameter Not available on

all chiller systems

PB (Time) Phase Balance Relay 5 Seconds Instantaneous Settings not recommended

For IQ500 Motor

Protection relay:

DIP Switches 5 & 6

To prevent chiller from tripping 6 seconds after a steady state current

imbalance of 50%

Set 5 and 6 to 1 and 1

Set other protection relays for same general function

For IQ 1000II Motor

Protection Relay:

Set point 32

Trip/Delay Phase Unbalance Function

I2T Trip Set other protection relays for same general function

36

Example Case Studies


Case Study MatrixCase No.

Customer Type Utility Chiller Manufacturer

Power Quality Issue(s)

1 Government Building(Nation Archives)

PEPCO Confidential Voltage SagsMomentary Interruptions

2 Bank City Public Service

Trane Voltage SagsMomentary Interruptions

3 Semiconductor Manufacturer

South East Asian Utilty

Confidential Voltage SagsMomentary Interruptions

4 General Manufacturing Iberdrola(Spain)

McQuay Voltage SagsMomentary Interruptions

5 General Manufacturing Lincoln Electric

McQuay Voltage Unbalance

6 General Manufacturing Louisville Gas and Electric

Carrier Voltage SagsMomentary InterruptionsVoltage Unbalance

7 Cosmetics Manufacturing

SRP York Voltage SagsMomentary InterruptionsVoltage UnbalanceHarmonics

8 General Manufacturing PSE&G Not disclosed Voltage SagsMomentary Interruptions

9 Commercial High Rise FPL Trane Voltage Unbalance10 Television Station FPL Trane Voltage Unbalance11 Community College FPL Trane Voltage Unbalance12 Church Memphis

Light, Gas and Water

Not disclosed Induced Flicker


Case Study Number 1: Chiller Voltage Sag/Momentary Outage Problems at Government Building Threatens Document Storage(summarized)

• Upgraded to new state of the art microprocessor controlled chillers

• Chillers found to trip off line 10 seconds after voltage sag event had cleared

• EPRI Worked with PEPCO to diagnose problem


Shutdown Sequence

2K2X “Ice Cube”

Relay

Interface toMicroprocessor


Shutdown Sequence

2K2X “Ice Cube”

Relay


Recommendations

•Add Voltage Conditioner, such a a Constant Voltage Transformer (CVT) on Control Power Circuit


Case Study #2: Chiller Control Panel Causes Shutdowns at Industrial Plant

• EPRI has Conducted Tests on Chillers at Suppliers Cooperate Engineering

• Tests Revealed Sensitive Relay in Compressor Starter Circuit

• Dropping out for deep sags and interruptions is typically preferred by customers to lower the likelyhood of mechanical damage

Single 2kVA Control Power Transformer Feeds Control Power and Oil Heater


Vulnerable Board Mounted “Ice Cube”relay, 1R drops out at about 69% of nominal, 1 cycle.

The Sensitive Component


• Move Heater Load Above Control Power Transformer and Install a CVT (as Shown).

• Hold in down to 40% Vnominal if sized properly

Recommendations: Option 1 CVT

CVT


Recommendation Option 2: VDC

• Option 2:Utilize a VDC to compensate down to 37% of nominal, but drop out for low voltages or interruptions.– 6T model holds in down

to 37% of nominal

VDC


Voltage Unbalance Case Studies

• Background For Voltage Unbalance Case Studies. All involved Trane chiller systems and have been provided by Florida Power and Light.

• Trane worked with FPL to implement to solve voltage unbalance incompatibilities between the utility system and the chiller control system.


Trane Control Panel Review

Panel Name Unbalance Tolerance

Black Classic 15% Current

UCP1 Dip Switch Selectable:- 15% Current if Enabled and chiller loaded >= 80%- Ignored if disabled (uses temperature sensors)

UCP2 Originally: Two settings,Factory Default: 15 % Current or 25% Current if selectedCurrently: 30 % non-defeatable Current


Case Study Number 3: Commercial high rise.

• Utilized Trane Chiller with early version of UCP2 control panel• Tripped at 10 to 15 % Current Unbalance• Trane adjusted trip calibration to 25%• No Customer Complaints of False Trips Since Change was

implemented.


Case Study Number 4:Television Station.

• Utilized early version of UCP2 control panel. • Measurements showed that chiller tripped at 2% voltage

unbalance, 13 to 16 percent current unbalance• Trane installed new control panel to change unbalance trip to

30%.


Review of Recommendations

• Protect Chiller Control Circuits from Voltage Sags– Relays, Motor Starter

Contactors• Make sure that Micro settings/or

hardwired controls have appropriate delays for detecting loss of voltage, current, and voltage unbalance

• Make sure that Micro settings are adjusted to allow for voltage unbalances of up to 3% and current imbalance from 18% to 30%.

• Set Chiller for Autorestart option if allowable.

• Remember to consider other loops such as chilled water, heat rejection, and airside in solution.

L1

L2

L3N

415/230Vor 6.6kV3 Phase

FU

M

CPT1

MSMS

ChillerController Motor

ProtectorRelay

M1

MC1

MC1

FU

M2

MC2

MC2

FU

M3

MC3

MC3

FU FU

FU

PLC

CPT2

CPT3 CPT4 CPT5

Chiller C

ompresser

Motor and Controls

Process Cooling

Water System

Controller

Chilled

Water Pumps

Condenser Water

Pumps Cooling

Tower Fans

CPT3Power

Conditioner

CPT4Power

Conditioner

CPT5Power

Conditioner

CPT2Power

Conditioner

CPT1Power

Conditioner

HOA HOA HOA

CR1

CR1

Chiller PQ Issues - EPRImydocs.epri.com/.../E232227_Chiller_PQ_Issues.pdf · · 2009-12-18Chiller...

Documents

Transcript of Chiller PQ Issues - EPRImydocs.epri.com/.../E232227_Chiller_PQ_Issues.pdf · · 2009-12-18Chiller...