ML20054L612

Sys Operators Procedures Manual 11.01,Power Sys Emergency Operation:Voltage Control Extra High Voltage Sys

ML20054L612
Person / Time
Site:	North Anna
Issue date:	05/26/1982
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
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ML20054L609	List: ML20054L608 ML20054L611 ML20054L612
References
11.01, NUDOCS 8207080296
Download: ML20054L612 (8)

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VIRGINIA ELECTRIC AND POWER COMPANY PAGE NO.

DATE ISSJED SYSTEM OPERATORS' PROCEDURES MANUAL 11.01 (1) 4/5/82 DATE REVISED CHAPTER: Power System Emergency Operation 5/26/82

SUBJECT:

Voltage Control E. H. V. System APPROVED SUBMITTED A. GENERAL

1. Maintaining voltages within safe operating limits is essential to reliable transmission system operation. This guide outlines basic considerations for the System Operator to follow in maintaining these voltage levels. The System Operators' authorities, responsibilities and required actions are also defined. Experience has shown that successful voltage control is dependent upon anticipating voltage trends and initiating corrective action before critical periods of heavy or light load are reached. The System Operator should therefore be aware of the importance of voltage control and the necessity to take action as soon as a potential problem is recognized.

2. System voltage levels are dependent on meeting the VAR requirements of the system. When a system is heavily loaded, lagging VARS are required from the system by the load. The sourcelag of these lagging VARS are generating units operating in the (overexcited) condition, putting VARS out of the units into the system. Additional sources of lagging VARS are static capacitor banks, and transmission line capacitance. During light load conditions a system may These VARS are coming experience an excessive amount of leading VARS.

from the system and must be absorbed by generating units operating in the lead (underexcited) condition, reactor banks, or synchronous condensers operating in the lead (underexcited) condition.

3. The reactive generating capability of transmission line capacitance is directly proportional to the square of the applied voltage. The reactive capability of the Mt. Storm-Morrisville line for example,As the varies from 218.5 MVARs at 525 KV to 178.9 MVARs at 475 KV. When the load on a line increases, its reactive losses also increase.

reactive losses equal the reactive generating gapability, the surge this impedance loading (SIL) of the line is reached. Loading beyond point creates a VAR deficiency which must be supplied by capacitor banks or generating units operating in the lag condition.

4. High voltage conditions increase a transmission line's reactive generating capability. The increased reactive tends to increase the voltage level in an amplifying manner. High voltage problems generally occur when the EHV system is lightly loaded and therefore has excessive leading vars. Corrective action for this condition would be an attempt to increase reactive losses of the network or decrease the reactive sources.

8207080296 820701 I PDR ADOCK 05000338 P PDR

DATE ISSUED VIRGINIA ELECTRIC AND POWER COMPANY PAGE NO.  !

4/5/82 SYSTEM OPERATORS' PROCEDURES MANUAL 11.01 (2)

DATE REVISED CHAPTER: Pcwer System Emergency Operation 5/26/82 SUBMITTED

SUBJECT:

Voltage Control E. H. V. System APPROVED A. 5. Although this guide primarily addresses the 500 KV system, the 230 KV system must also be monitored. It is doubtful that sustained voltage excursions will be present on the 230 KV system and not on the 500 KV system. However certain local conditions could cause such a situa-tion. If the 230 KV system is outside its alarm points (219 KV to 246 KV) appropriate steps should be taken to return the voltage to the proper level. The high level alarm for Surry Power Station is set at 240 KV.

B. NORMAL CONDITIONS

1. Primary system voltage control should be accomplished using only controllable reactive sources including generating units, hydro units operating as synchronous condensers, bus capacitors and bus reactors.

2. Secondary system voltage control can be used to balance or trim system voltages only after primary control has been fully utilized.

' Secondary control should be accomplished using transformer LTC tap changers.

C. LOW VOLTAGE CONDITIONS

1. The System Operator should recognize the potential for, or development of, a low voltage condition and take steps to prevent equipment damage and/or an uncontrolled area shutdown. If bus voltages are low and allowed to continue decaying, the VAR output of l the system capacitor banks and transmission lines is reduced. The resulting VAR deficiency must be supplied by generating units operating in the lag condition, often at the expense of MW output.

This process, if allowed to continue would eventually reach the point where generating units would reach their VAR output limits, the output of other VAR sources would continue to decrease, and the voltage would continue a steady decline,

a. Slow voltage Decay Procedure (Apparent load build up towards peak and lack of generation support.)

(1.) The low voltage alarm points for the data acquisition computer are set at 510 KV at the N' orth Anna and Surry busses, and at 475 KV throughout the rest of the 500 KV system. The critical voltage at North Anna and Surry is 505 KV. Refer to Section E. for specific instructions involving

e e VIRGINIA ELECTRIC AND POWER COMPAN" PAGE NO.

DATE ISSUED 4/5/82 SYSTEM OPERATORS' PROCEDURES MANUAL 11.01 (3)

I DATE REVISED CHAPTER: Power System Emergency Operation 5/26/82 i SUBMITTED

SUBJECT:

Voltage Control E. H. V. System APPROVED

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C. 1. a. (1.) nuclear stations. When an initial alarm is generated, (con't) immediate action should be taken to reverse the trend and restore the voltage to normal, or scheduled, levels. The data acquisition computer is programmed to alarm at the set point and initiate a " low limit exceeded" message. Action must be taken at this point to reverse the trend. If the voltage decay continues beyond this limit and exceeds one percent of the alarm setting a second message will be generated indicating an " exceeded one percent significance alarm level" message. If the second alarm level is reached all actions within the authority of the System Operator (as outlined in this procedure) must be executed as expeditiously as possible. When the first alarm level is reached proceed with each of the following steps until the voltage is established above the alarm setting. System conditions may alter the actual order of these steps.

(2.) Check that the reactor banks at Surry, North Anna, and Carson are out of service. If not, arrange to have them de-energized as quickly as possible. The Carson bank may be operated by supervisory control from the System Operation Center. Plant personnel must be contacted at North Anna and Surry to operate those banks.

(3.) Check that all transmission voltage capacitor banks are in service. If not arrange to have them switched on as quickly as possible.

(4.) Contact all power stations to insure each unit on line is operating in the maximum permissible lag condition. If stations cannot maintain their voltage schedules, request an explanation and make note of it in the System Operators' Log.

(5.) Raise generation levels on units in the low voltage area (or in an area which could provide some improvement in the 2 voltage level) to reduce power transf ers and hence the 1 X losses.

(6.) Request interconnected companies to take all steps possible to help maintain system voltage schedules. Suggested steps include 1) increasing voltage levels on the interconnected system, 2) making additional transactions with Vepco that may improve system voltages, or 3) changing transaction schedules with other systems that may be contributing to the Vepco problem.

DATE ISSUED VIRGINIA ELECTRIC AND POWER COMPANY PAGE NO.

4/5/82 SYSTEM OPERATORS' PROCEDURES MANUAL 11.01 (4)

DATE REVISED CHAPTER: Power System Emergency Operation 5/26/82 SUBMITTED

SUBJECT:

Voltage Control E. H. V. System APPROVED C. 1. a. (7.) Start additional units in the low voltage area to supply reactive and. red,uce power transfers.

(8.) If steps C.1.a. (1. ) through C.1.a. (7.) fail to improve the voltage situation notify the System Operation Duty Supervisor or the Chief System Operator.

Note: If system voltages continue to decline the next step will be implementation of the Company's Load Curtailment Program (Section 17.05 Vepco Policy and Procedures Manual). The Manager-Power Supply will decide when and to what extent load curtailment is required. He will select the plan or combination of plans necessary to achieve the required curtailment and will notify the appropriate regulatory agencies of the load curtailment action taken.

b. Rapid Voltage Decay Procedure (Sudden loss of large blocks of generation).

(1.) In cases of extreme emergency, where lead must be shed quickly, the Senior System Operator will determine the need for immediate implementation of Plan III - Phase A of the Load Curtailment Program and will shed load directly from the '

System Operation Center through the division SCADA systems.

Either one or both of two 600 MW increments may be shed.

(2.) Immediately following an emergency SCADA implemented load curtailment from the System Operation Center, the Senior System Operator will advise the Division Operation Centers and the Chief System Operator of the action taken. The Chief System Operator will notify the Manager-Power Supply who will then notify the Manager-Division Services and the Manager-Communications.

l (3.) In emergency situations where there is time to notify the divisions, the Senior System Operator will determine the l

' need for implementation of Plan III - Phase A and will issue orders to execute the plan directly to the appropriate Division Operating Managers, or their designated l

i representatives, specifying the number of load increments to be shed. .

f (4.) As the SCADA systems continue to be expanded, there will be a continuing increase in the nu=ber of SCADA controlled circuits available for rotational interruptions. SCADA controlled circuits should be used along with =anually l

controlled circuits with the provision that at least four (4) incre=ents of load are available for quick curtailment by other SCADA controlled circuits.

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DATE ISSUED VIRGINIA ELECTRIC AND POWER COMPANY PAGE NO.

4/5/82 SYSTEM OPERATORS' PROCEDURES MANUAL 11.01 (5)

DATE REVISED CHAPTER: Power System Emergency Operation 5/26/82 SUBMITTED

SUBJECT:

Voltage Control E. H. V. System APPROVED C. 1. b. (5.) The Chief System Operator will advise the Manager-Power Supply of the action taken and he will then notify the Manager-Division Services and Manager-Communications.

(6.) When manual load shedding instructions are executed, each District Manager vill immediately issue the appropriate press release.

(7.) When the need for load curtailment is past, the System Operator will issue service restoration instructions directly to the appropriate Division Operating Managers, or their designated representatives. Loads will be restored only in the amounts and at the times specified by the System Operator.

(8.) The Chief System Operator will advise the Manager-Power Supply of the action taken and he will then notify the Manager-Division Services and Manager-Communications.

D. HIGH VOLTAGE CONDITIONS

1. During light load conditions, unacceptably high voltages may exist on the EHV system. If bus voltages are high, the VAR output of system capacitor banks (if lef t in service) and transmission line capacitance is increased. The resulting VAR surplus must be absorbed by generat-ing units or synchronous condensers operating in the lead condition.

If left unchecked this condition could result in generating units reaching their VAR intake capabilities, loss of major VAR absorbing units and a further compounding of the problem. High voltage conditions may be particularly prevalent if several major units are out of service during light load periods or if the generating units are not operating at their maximum lead condition.

a. The high voltage alarm points for the data acquisition computer are set at 530 KV at the North Anna and Surry busses, and at 535 KV throughout the rest of the 500 KV system. The critical voltage at North Anna and Surry is 535 KV. Refer to Section E. for specific instructions involving nuclear stations. When an initial alarm is generated i= mediate action should be taken to reverse the trend and restore the voltage to normal, or scheduled levels. The data acquisition computer is progra=med to alarm at the set point and initiate a "high limit exceeded" message. Action must be taken at this point to reverse the trend. If the voltage rise continues beyond this limit and exceeds one percent of the alarm setting a second message will be generated indicating an " exceeded one percent significance alarm level" message. If the second alarm level is reached all actions within the authority of the System Operator (as outlined in this procedure) must be executed S

. g DATE ISSUED VIRGINIA ELECTRIC AND POWER COMPANY PAGE NO.

4/5/82 SYSTEM OPERATORS' PROCEDURES MANUAL 11.01 (6)

DATE REVISED CHAPTER: Power System Emergency Operation 5/26/82 SUBMITTED

SUBJECT:

Voltage Control E. H. V. System APPROVED D. 1. a. as expeditiously as possible. When the first alarm level is (cont ' t) reached proceed with each of the following steps until the voltage is established below the alarm setting. System conditions may alter the actual or_ der of these steps.

b. Check that all transmission voltage capacitor banks are out of service. If not, arrange to have them switched out as quickly as possible.

c. Check that the reacter banks at Surry, North Anna, and Carson are in service. If not, arrange to have them switched on as quickly as possible. The Carson bank may be operated by supervisory control from the System Operation Center. Plant personnel must be contacted at North Anna and Surry to operate those banks.

Note: Under certain operating conditions at Surry the reactor banks may cause an overload on one of the transformers feeding the 34.5 KV bus. This conditien is alarmed in the System Operation Center. If this alarm is received, the plant should be notified immediately so that the overload condition can be corrected,

d. Contact all power stations to insure each unit on line is operating in the maximum permissible lead condition. If stations cannot maintain their voltage schedules request an explanation and make note of it in the System Operator's Log.

e. Check with the interconnected companies to make certain they are operating in maximum lead condition and are on voltage schedule.

f. Instruct Roanoke Rapids operators to operate Roanoke Rapids and Gaston units (where possible) as synchronous condensers in the maximum lead condition.

g. Have a switchman sent to Mt. Storm switchyard. Open the Mt. Storm end of line no. 572. As soon as possible af ter the Mt. Storm end is opened, open the Morrisville end of line no. 572 by supervisory control from the System Operation Center. Arrange to have breaker disconnects opened as soon as possible after the breakers are opened.

h. If the voltage continues to rise or does not drop below the alarm point, open the Surry-Carson line no. 562 at the Surry end followed as quickly as possible at the Carson end. Arrange to have breaker disconnects opened as soon as possible after the breakers are opened.

M DATE ISSUED VIRGINIA ELECTRIC AND POWER COMPANY PAGE NO.

4/5/82 SYSTEM OPERATORS' PROCEDURES MANUAL 11.01 (7)

DATE REVISED CHAPTER: Power System Emergency Operation 5/26/82 SUBMITTED

SUBJECT:

Voltage Control E. H. V. System APPROVED D. 1. 1. If the voltage continues to rise or does not drop below the alarm point, open the Ladysmith-Ox line no. 552 at the Ladysmith end followed as quickly as possible at the Ox end. Arrange to have breaker disconnects opened as soon as possible after the breakers open,

j. If steps D.1.a. through D.1.1. fail to improve the voltage situation notify the System Operation Duty Supervisor or Chief System Operator.

Note: Further attempts to reduce system voltages may involve reduction of generation and/or removal of certain units from service. The Manager-Power Supply will determine when and to what extent additional action is required.

E. SPECIFIC INSTRUCTION - NUCLEAR POWER STATIONS

1. Due to voltage restrictions at the nuclear power stations the Station Operators at Surry and North Anna will be following a station voltage control procedure prior to reaching the System alarm points.

a. When the voltage schedule cannot be met because of Station limita-I tions, the Station Operator will contact the System Operator.

! Record the deviation and limiting factor in the System Operators' Log.

b. When all measures defined in the station voltage control procedure have been utilized and the station voltage cannot be maintained between 512 KV and 528 KV (222KV and 238KV on the Surry 230KV bus) the Station Operator will contact the System Operator.

Record in the System Operators' Log and if the System alarm limits (510 KV or 530 KV) are reached begin implerentation of the appropriate procedure to acsist in the cort.ction of the condition. All measures must be taken to avoid the limits of 505 KV or 535 KV at the nuclear stations.

c. When the voltage regulator is being operated'in the manual mode, the Station Operator will contact the System Operator. Record this condition and the reason for it in the System Operators' Leg.

! d. Before reactor banks are removed from or placed in service, the Station Operator will contact the System Operator. Record all reactor bank switching in the System Operators' Log.

. /g-DATE ISSUED VIRGINIA ELECTRIC AND POWER COMPANY PAGE NO.

4/5/82 SYSTEM OPERATORS' PROCEDURES MANUAL 11.01.(8)

DATE REVISED CHAPTER: Power System Emergency Operation 5/26/82 SUBMITTED

SUBJECT:

Voltage Control E. H. V. System APPROVED E. 1. e. When the voltage regulator is being operated in the automatic mode and adhering to the. voltage schedule requires operating a unit beyond its safe operating limit curve, the Station Operator will notify the System Operator. Station personnel will decide whether to go beyond this limit based on current station equipment status.

Record in the System Operator's Log the fact that the limit has been reached, whether the station has decided to go beyond this '

limit, and if so, the steady state limits reached aiter the adjustment has been made,

f. k*nen the voltage regulator is being operated in the manual mode and adhering to the voltage schedule requires operating beyond its safe operating limit curve, the Station Operator will contact the System Operator. Operation beyond this limit in the manual mode can only be authorized by the System Operator. Record the fact that the limit has been reached in the System Operators' Log.

Current instructions are not to operate a unit beyond its safe operating limit while the voltage regu.'4 tor is in the manual mode.

Caution: kten operating a unit in the lead condition (ie. taking MVARs in), the MVAR limit shall be governed by the " safe operating limit" on the generator capability curve. This is a conservative limit for underexcited operation. Below this limit, there is the MEL (minimum excitation limiter) characteristic and the KLF (loss of field relay) characteristic. The MEL is a protective feature internal to the voltage regulator which will limit exciter field current to a pre-determined level only when the regulator is operated in automatic. If the regulator is operated in manual the MEL unit is not functional and operation below the " safe operating limit" could result in a KLF operation and unit trip without prior alarm.

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