GE L60, Инструкция по эксплуатации

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CHAPTER 8: APPLICATION OF SETTINGS 87PC PHASE COMPARISON ELEMENT
L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL 8-3
8
87PC CH1 DELAY and 87PC CH2 DELAY
These settings are made in the field to be equal to the sum of three delays; symmetry adjustment, propagation time of the
line and receiver. Different methods can be used.
The L60 allows the customer to check and set phase delay without using an oscilloscope and by means of FlexLogic
operands and applying the corresponding current to both relays. Oscillography shows the time difference (including PLC
delay and line propagation time) between local and remote signals. Moving cursors and measuring an average from a few
points time, the user can determine and apply the proper setting.
87PC STABILITY ANGLE
The stability angle setting must accommodate the security requirements for the external fault and dependability
requirements for the internal fault. Default value 3 ms corresponds to about 65 degrees of blocking zone for a 60 Hz
system. It overrides sources angular shift resulting from load, charging current, CT errors, and so on.
The stability angle js can be estimated as follows:
φ s = φ load + φ capac + φ ct Eq. 8-1
where
φ load is a sources angular shift phase between the line terminal at maximum expected load, expressed in electrical
degrees
φ capac is the capacitive current compensation angle evaluated as φ capac = arctan (Icapac / IFDH) expressed in electrical
degrees, where Icapac is a line capacitive current and IFDH is the setting of FDH (fault detector high).
φ ct is the CTs error and saturation compensation angle and can be adopted as equal 10° for most cases unless there is a
special consideration or concern. For such cases φ ct can be increased up to 20°.
87PC TRANS BLOCK PICKUP
This setting is used to increase security during and after clearing of an external fault and to prevent false tripping during
current reversals. Set the setting higher than the time difference in operation between FDH and output from the
coincidence discriminator. A of setting 10 to 30 ms gives sufficient security for most conditions.
87PC TRANS BLOCK RESET
This setting is used to reset transient blocking and allow tripping. According to local conditions, setting should be
considered as the sum of protection operating time and breaker opening time of the adjacent line and minus the Transient
Pickup value to override uncertainty during clearing external faults. The faster the fault clearing at the adjacent line, the
lower setting can be applied.
Ttr_rst = Tpr Tbreak_adj – Ttr_pkp Eq. 8-2
where
Tprot_adj is the expected time of main protection operation on the adjacent line
Tbreak_adj is the operation time of the breaker on the adjacent line
Ttr_pkp is selected Transient Pickup time
87PC BLOCK
Some cases can be defined when blocking of the phase comparison scheme is required. This setting blocks the tripping
function. PLC alarm contacts indicating channel failure are usually assigned for this setting, especially in blocking schemes.
87PC CHNL LOSS TRIP WINDOW
This setting is applicable to the 2TL-BL-DPC-2FL scheme only. The typical setting is 150 ms.
8.1.3 Settings example
Consider the following setup:
•
Single-circuit 765 kV line