7.3 Voltage Emergencies

Question 1

What are the 3 procedures used for heavy system loads or voltages approaching limits?

Answer 1

• Low Voltage Alert
• Heavy Load Voltage Schedule Warning
• Heavy Load Voltage Schedule Action

Question 2

What is the purpose of the Low Voltage Alert?

Answer 2

Heighten awareness, increase planning analysis for an anticipated heavy load / low voltage operation period

Question 3

What are some of PJM’s actions during a Low Voltage Alert?

Answer 3

• Conduct power flow analysis of future load / transfer increases
• Review outages
• Prepair to curtail transactions
• Use IDC, may invoke NERC TLR process
• Request Reactive Reserve Check (RRC)

Question 4

What are PJM Member actions during a Low Voltage Alert?

Answer 4

• Notify key personnel
• Defer maintenance and testing
• Respond to Reactive Reserve Check

Question 5

What is the purpose of the Heavy Load Voltage Schedule Warning?

Answer 5

To prepare for maximum support of voltages on the BES.

Question 6

What are PJM actions during a Heavy Load Voltage Schedule Warning?

Answer 6

• Issue the warning 4 hours prior to requesting implementation of the HLVS
• Request members to verify all actions have been taken on the distribution and sub transmission level to support voltage at the EHV level.

Question 7

What are PJM Member actions during a Heavy Load Voltage Schedule Warning?

Answer 7

Ensure the following: 
 \+ Reactors are out of service
\+ Capacitors are in service
\+ Trafo taps are adjusted to ensure all dist. caps in service
- All AVRS are in service

Question 8

What is the purpose of a Heavy Load Voltage Schedule Action?

Answer 8

Issues at peak load periods for max support of voltage on the BES and to increase reactive reserves at the EHV level.

Question 9

What are PJM actions during a Heavy Load Voltage Schedule Action?

Answer 9

• Request all members implement HLVS

- Cancel when appropriate

Question 10

What are PJM Member actions during a Heavy Load Voltage Schedule Action?

Answer 10

Same as warning, plus:
- Units on 230 kV system and below increase MVAR output to maintain greater of scheduled or nominal bus voltages.

• Units on 500kV+ system operated to maintain a reasonable MVAR reserve.
• Inform PJM of any units approaching max MVAR output, MVAR restrictions, or AVRs out of service.

Question 11

What is the purpose of a High System Voltage message?

Answer 11

To prepare the system for expected high voltages during a light load period.

Question 12

What are PJM’s actions during a High System Voltage condition?

Answer 12

• Issue HSV message
• Direct companies to remove switchable caps and insert switchable reactors.
• Ensure generators, synchronous condensers, and SVCs are within their zone to absorb reactive power.
• Request neighboring BA’s to assist
• Adjust 500 /230kV taps
• PJM has identified several ckts that have been effective in controlling high voltage when removed from service.

Question 13

Member actions during High System Voltage conditions:

Answer 13

• TO’s may request adjustments to generator excitation to absorb reactive power
• Generation should operate at lower end of voltage schedule
• Voltage schedule / excitation adjustments outside of schedule should be coordinated with PJM.
• Generation will communicate with PJM & TO if ability to absorb MVARs differs from reported capability.