Bank Phase Overvoltage Settings - GE C70 Instruction Manual

CHAPTER 8: APPLICATION OF SETTINGS
The pickup setting for the stage 2 current unbalance trip element is specified as the unbalance current during maximum
system conditions midway between the third and fourth capacitor element failure unbalance currents.
Therefore, the trip delay is chosen 50 ms.

8.4.7 Bank phase overvoltage settings

To protect the capacitor bank from overvoltage resulting from abnormal system conditions, the capability of the bank to
withstand transient overvoltages must be evaluated according to the IEEE 1036-1992 standard or to manufacturer
specifications. For example, consider the following manufacturer overvoltage data:
• 2 pu overvoltage toleration for 0.25 second
• 1.5 pu overvoltage toleration for 15 seconds
• 1.25 pu overvoltage toleration for 5 minutes
When the relay settings are calculated, the number of prospective overvoltage transients stressing the capacitor insulation
during the bank lifetime must be taken into account. As such, it is preferable to set the relay conservatively.
C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL
SETTINGS EXAMPLE
Eq. 8-26
8
8-19