•
For the synchronous machines as the generator in Table
, the transient reactance Xd'
shall be used. This due to the relatively slow electromechanical oscillations under out-of-
step conditions.
•
Sometimes the equivalent resistance of the generator is difficult to get. A good estimate
is 1 percent of transient reactance Xd'. No great error is done if this resistance is set to
zero (0).
•
Inclination of the Z-line, connecting points SE and RE, against the real (R) axis can be
calculated as arctan ((
Re ForwardX) / (Re ForwardR)), and is for the case
equal to 84.55 degrees, which is a typical value.
Other settings:
•
ReachZ1: Determines the reach of the zone 1 in the forward direction. Determines the
position of the X-line which delimits zone 1 from zone 2. Set in % of
ForwardX. In the case
, where the reactance of the step-up power transformer is 11.32 % of the
total
ForwardX, the setting ReachZ1 should be set to ReachZ1 = 12 %. This means that the
generator – step-up transformer unit would be in the zone 1. In other words, if the centre
of oscillation would be found to be within the zone 1, only a very limited number of pole-
slips would be allowed, usually only one.
•
StartAngle: Angle between the two equivalent rotors induced voltages (that is, the angle
between the two internal induced voltages E1 and E2 in an equivalent simplified two-
machine system) to get the start signal, in degrees. The width of the lens characteristic is
determined by the value of this setting. Whenever the complex impedance Z(R, X) enters
the lens, this is a sign of instability. The angle recommended is 110 or 120 degrees,
because it is at this rotor angle where problems with dynamic stability usually begin.
Power angle 120 degrees is sometimes called “the angle of no return” because if this angle
is reached under generator swings, the generator is most likely to lose synchronism. When
the complex impedance Z(R, X) enters the lens the start output signal (
START
) is set to 1
(
TRUE
).
•
TripAngle: The setting TripAngle specifies the value of the rotor angle where the trip
command is sent to the circuit breaker in order to minimize the stress to which the
breaker is exposed when breaking the currents. The range of this value is from 15° to 90°,
with higher values suitable for longer breaker opening times. If a breaker opening is
initiated at for example 60°, then the circuit breaker opens its contacts closer to 0°, where
the currents are smaller. If the breaker opening time
tBreaker is known, then it is possible
to calculate more exactly when opening must be initiated in order to open the circuit
breaker contacts as close as possible to 0°, where the currents are smallest. If the breaker
opening time
tBreaker is specified (that is, higher than the default 0.0 s, where 0.0 s
means that
tBreaker is unknown), then this alternative way to determine the moment
when a command to open the breaker is sent, is automatically chosen instead of the more
approximate method, based on the
TripAngle.
•
tReset: Interval of time since the last pole-slip detected, when the Out-of-step protection
is reset. If there is no more pole slips detected under the time interval specified by
tReset
since the previous one, the function is reset. All outputs are set to 0 (
FALSE
). If no pole slip
at all is detected under interval of time specified by
tReset since the start signal has been
set (for example a stable case with synchronism retained), the function is as well reset,
which includes the start output signal (
START
), which is reset to 0 (
FALSE
) after
tReset
interval of time has elapsed. However, the measurements of analogue quantities such as
R, X, P, Q, and so on continue without interruptions. Recommended setting of
tReset is in
the range of 6 to 12 seconds.
•
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
,
the number of allowed pole slips in zone 2 can be the same as in zone 1. Recommended
value:
NoOfSlipsZ2 = 2 or 3.
1MRK 505 343-UEN B
Section 7
Impedance protection
393
Application manual
Содержание Relion 670 series
Страница 1: ...RELION 670 SERIES Line differential protection RED670 Version 2 1 IEC Application manual...
Страница 2: ......
Страница 40: ...34...
Страница 64: ...58...
Страница 150: ...144...
Страница 406: ...400...
Страница 472: ...466...
Страница 494: ...488...
Страница 512: ...506...
Страница 524: ...518...
Страница 604: ...598...
Страница 686: ...680...
Страница 718: ...712...
Страница 722: ...716...
Страница 758: ...752...
Страница 759: ...753...