The reach of the first impedance zone of the distance protection function is normally set for values less than 100%. Protective signaling is used to extend protection to 100% of the section. This is achieved by logical linking of the signals that are transmitted by the remote station’s protection device.
In order for protective signaling (PSIG) to function, the following requirements must be satisfied:
¨ It must be activated.
¨ There must be no external block.
¨ There must be no transmission fault.
¨ The function PSIG: Receive EXT must be configured to a binary signal input.
Protective signaling can be activated or deactivated from the local control panel.
Once protective signaling is ready, distance protection timer stage t1 is blocked. A trip enable in distance protection zone 1 is then issued after the protective signaling tripping time has elapsed.
41 Protective signaling tripping time
A communication malfunction or failure leads to a
protective signaling block. If protective signaling is carried out by a signal transmission or communication device, the device’s fault signal can be connected. In the case of protective signaling via pilot wires or in the operating mode referred to as "reverse interlocking," an internal monitoring function detects any fault in the communication channel. Protective signaling can be operated in seven different modes. The following operating modes require a signal transmission device:
¨ Direct transfer trip underreaching
¨ Permissive underreaching transfer tripping (PUTT)
¨ Zone extension
¨ Signal comparison release scheme
¨ Signal comparison blocking scheme
For operation in the mode referred to as "Signal compari- son pilot wire," pilot wires are required for signal trans- mission.
P S I G : O p e r a t i n g m o d e "Direct transfer trip underreaching"
When there is a “Distance trip zone 1" a signal is sent to the remote station’s protection device. Upon receipt of the signal by the remote station, the remote station’s circuit breaker is tripped.
P S I G : O p e r a t i n g m o d e "Permissive underreaching transfer tripping (PUTT)”
With a "Distance trip zone 1" a signal is sent to the remote station’s protection device. Upon receipt of the signal by the remote station, the remote station’s circuit breaker is transfer tripped as a function of starting.
P S I G : O p e r a t i n g m o d e "Zone extension"
With "Distance trip zone 1" a signal is sent to the remote station’s protection device. Upon receipt of the
transmitted signal the measuring range of zone 1 in the remote station is increased by the zone extension factor kze HSR. If the fault lies within the extended zone, the remote station’s protection device also decides in favor of “Distance trip zone 1.”
43 Reaches with zone extension
(broken line: measuring range increased by the zone extension factor kze HSR)
P S I G : O p e r a t i n g m o d e “Signal comparison release scheme"
In the idle state the measuring range of zone 1 in both protection devices is extended by the zone extension factor kze HSR. The “Distance trip zone 1” of both protection devices is blocked.
If distance protection starting begins and the fault lies in the forward direction, a signal is sent to the remote station. In the event of a fault, both protection devices measure by using the normal measuring range and the range
extended by the zone extension factor kze HSR. A trip enable is issued if one of the following conditions is satisfied after the distance protection timer stage t1 has elapsed:
44 Zone reaches with the release scheme
(broken line: measuring range extended by the zone extension factor kze HSR)
If both zone extension factors (kze P-G HSR and kze P-P HSR) are set at a value of "1.0," a trip enable is issued only if the second of the conditions given above is satisfied.
In the event of a change in direction the received signal is ignored for 80 ms (“transient blocking”) so that false tripping will not occur in double line protection.
P S I G : O p e r a t i n g m o d e "Signal comparison blocking scheme"
In the idle state the measuring range of zone 1 in both protection devices is extended by the zone extension factor kze HSR. The “Distance trip zone 1” of both protection devices is enabled.
If distance protection starting begins and the fault lies in the backward direction, a signal is sent to the remote station.
In the event of a fault, both protection devices measure by using the normal measuring range and the range
extended by the zone extension factor kze HSR. A “Distance trip zone 1” can be issued instantaneously (t0)
45 Zone reaches with the blocking scheme
(broken line: measuring range extended by the zone extension factor kze HSR)
If both zone extension factors (kze P-G HSR and kze P-P HSR) are set at a value of "1.0," a trip is only possible after t1 has elapsed.
P S I G : O p e r a t i n g m o d e "Signal comparison pilot wire"
To form the communication link it is necessary to connect either the break contact or the make contact of the transmitting relay, depending on the transmitting relay mode selected (Transm. relay make contact or Transm. relay break contact), to the P S I G : R e c e i v e E X T input of the remote station by means of pilot wires. In the idle state there is a received signal in both protection devices (DC loop closed), and the measuring range of zone 1 is extended by the zone extension factor
kze HSR. The “Distance trip zone 1” of both protection devices is enabled.
If distance protection starting begins and a fault lies in the backward direction or if the overcurrent starting originates from the distance protection starting, then a signal is sent to the remote station without delay.
In the event of a fault both protection devices measure by using the normal measuring range and the measuring range extended by the zone extension factor kze HSR. A “Distance trip zone 1” can be issued instantaneously (t0) with the normal reach. The “Distance trip zone 1” is blocked if the following conditions are satisfied simultane- ously after distance protection timer stage t1 has elapsed:
¨ The fault lies within the extended measuring range.
¨ A transmitted signal is received by the remote station. If both zone extension factors (kze P-G HSR and
kze P-P HSR) are set at a value of "1.0," a trip is only possible after t1 has elapsed.
The pilot wires are monitored for interruptions. If, during fault-free operation, that is, when there is no distance protection starting, no signal is received by the remote station for a period longer than the set transmitted signal reset time plus 600 ms, then a P S I G : T e l e c o m . f a u l t y signal (see Figure 42) is issued, and protective signaling is blocked.
P S I G : O p e r a t i n g m o d e "Reverse interlocking"
In radial networks with infeed from a single end it is possible under certain conditions for busbar protection to be configured by sampling the starting of feeder protection devices. By means of appropriate interconnection, a send signal is then formed when a feeder protection device starts. The receipt of this signal by the PD 521 blocks the “Distance trip zone 1.” The blocking signal reset is delayed by approximately 80 ms.
The pilot wires are monitored. If a received signal is present for more than 10 s without any distance protection starting, then the distance trip zone 1 block is canceled. A new block cannot occur until the received signal has dropped out.
47 Reverse interlocking
Echo Function
It is possible to select "without or with" echo on receive. This setting is only active in the following modes:
¨ PUTT (permissive underreaching transfer trip)
¨ Zone extension
¨ Signal comparison release scheme
¨ Signal comparison blocking scheme
If the "with" echo setting is selected, a signal is sent to the remote station if the received signal is present for more than 50 ms and no “distance protection starting” is active.
The further transmission of a received signal as a send signal is then blocked for 20 s. This prevents a
permanent signal from being transmitted.
Testing the Communication Channel
The communication link can be tested. For this purpose a 500 ms send signal is issued through a binary signal input or the integrated local control panel. The remote station receives this signal if the transmission section is OK. In the mode referred to as "Direct transfer trip underreach" no test is possible, since a received signal will immediately lead to a “Trip” in the remote station. Likewise, testing is not possible with the "Reverse interlocking" setting.