Hitachi Relion 670 Series Applications Manual page 114

Section 7
Impedance protection
• NoOfSlipsZ1: Maximum number of pole slips with centre of electromechanical oscillation within zone
1 required for a trip. Usually, NoOfSlipsZ1= 1.
• NoOfSlipsZ2: Maximum number of pole slips with centre of electromechanical oscillation within zone
2 required for a trip. The reason for the existence of two zones of operation is selectivity, required
particularly for successful islanding. If there are several pole slip (out-of-step) relays in the power
system, then selectivity between relays is obtained by the relay reach (for example zone 1) rather
then by time grading. In a system, as in Table 13, the number of allowed pole slips in zone 2 can be
the same as in zone 1. Recommended value: NoOfSlipsZ2 = 2 or 3.
• Operation: With the setting Operation OOSPPAM function can be set On/Off.
• OperationZ1: Operation zone 1 Enabled, Disabled. If OperationZ1 = Disabled, all pole-slips with
centre of the electromagnetic oscillation within zone 1 are ignored. Default setting = Enabled. More
likely to be used is the option to extend zone 1 so that zone 1 even covers zone 2. This feature is
activated by the input to extend the zone 1 (EXTZ1).
• OperationZ2: Operation zone 2 Enabled, Disabled. If OperationZ1 = Disabled, all pole-slips with
centre of the electromagnetic oscillation within zone 2 are ignored. Default setting = Enabled.
• tBreaker: Circuit breaker opening time. Use the default value tBreaker = 0.000 s if unknown. If the
value is known, then a value higher than 0.000 is specified, for example tBreaker = 0.040 s: the out-
of-step function gives a trip command approximately 0.040 seconds before the currents reach their
minimum value. This in order to decrease the stress imposed to the circuit breaker.
• VBase: This is the voltage at the point where the Out-of-step protection is installed. If the protection
is installed on the generator output terminals, then VBase is the nominal (rated) phase to phase
voltage of the protected generator. All the resistances and reactances are measured and displayed
referred to voltage VBase. Observe that ReverseX, ForwardX, ReverseR, and ForwardR must be
given referred to VBase. IBase is the protected generator nominal (rated) current, if the Out-of-step
protection belongs to a generator protection scheme.
• InvertCTCurr: If the currents fed to the Out-of-step protection are measured on the protected
generator neutral side (LV-side) then inversion is not necessary (InvertCTCurr = Disabled), provided
that the CT's orientation complies with Hitachi Energy recommendations, as shown in Table 13.If the
currents fed to the Out-of-step protection are measured on the protected generator output terminals
side (HV-side), then invertion is necessary (InvertCTCurr = Enabled), provided that the CT's actual
direction complies with Hitachi Energy recommendations, as shown in Table 13.
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1MRK511407-UUS Rev. N
Phasor measurement unit RES670
Application manual