Section 7
Impedance protection
NoOfSlipsZ1 : Maximum number of pole slips with centre of electromechanical oscillation
•
within zone 1 required for a trip. Usually,
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 12, the number of
allowed pole slips in zone 2 can be the same as in zone 1. Recommended value:
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 =
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 =
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
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
phase to phase voltage of the protected generator. All the resistances and reactances are
measured and displayed referred to voltage
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 (
provided that the CT's orientation complies with ABB recommendations, as shown in Table 12.
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 (
provided that the CT's actual direction complies with ABB recommendations, as shown in
Table 12.
108
NoOfSlipsZ1 = 1 .
VBase is the nominal (rated)
VBase . Observe that ReverseX , ForwardX ,
InvertCTCurr = Enabled ),
1MRK 511 364-UUS A
NoOfSlipsZ2 =
Enabled .
Enabled .
tBreaker = 0.040 s :
InvertCTCurr = Disabled ),
Application manual