Location
Odenkirchener Str. 201, 41236 Mönchengladbach
Year
From 2010 to the present
Products
FW-5, FW-50
Protocol
IEC 60870-5-101, IEC 60870-5-103, IEC 60870-5-104
In the NEW-Netz-GmbH medium-voltage network, the neutral point is operated in a compensated manner. For depth location in the event of an earth fault, short-time earthing is used in addition to pulse location in a sub-region. With short-time earthing, in the event of an earth fault, the neutral point is earthed via a resistor for 80 milliseconds. This is sufficient to excite the short circuit indicators situated in the network. The site of the fault can then be located on the basis of the excitation.
The net-line FW-5 and its integrated soft PLC codeIT are used to control the short-time earthing. The short-time earthing can be controlled and monitored both on site and via a control link by the central control station.
Short-time earthing can be started as a single event automatically when an earth fault occurs by monitoring of the e-n voltage or also multiple times during manual operation by the control centre personnel or the personnel on site. During the short-time earthing cycle, the change in state of the circuit breaker is monitored.
The information from a short circuit indicator is used to check in the single-pole branch of the resistor whether the single-pole short circuit current is sufficient to excite the short circuit indicators in the network and the short-time earthing was successful. If the single-pole short circuit current is not sufficient, the message “short time earthing failed” is signalled and the short-time earthing can be started again in manual mode.
The readiness and the state of the circuit breaker and the short-time earthing, and the states of the switch-isolators are monitored. A malfunction is signalled to the central control station and at the same time the short-time earthing is blocked.
In the event that the circuit breaker does not interrupt the short-time earthing after the 80 milliseconds set, the 110 kV circuit breaker is switched off after a set time by monitoring the current through the resistor, and this is signalled to the central control station.
The message “CB permanently on” signals to the central control station that the circuit breaker of the short-time earthing is permanently switched on. This is necessary for maintenance purposes. However, during normal operation it is absolutely necessary to switch off the corresponding transformer, since the medium-voltage network would otherwise be operated earthed at a low resistance.
As there is thermal loading of the resistor during each short-time earthing, a thermal image of the resistor is stored in the PLC. This should protect the resistor from thermal damage. When the maximum permissible number of short-time earthing operations is reached, the control system blocks further short-time earthing operations from being set up and signals this to the central control station. The number of short-time earthing operations still permissible is indicated to the switchgear personnel of the central control station.
Further use of SAE components at NEW Netz
13 x net-line FW-50-14 in substations
86 x net-line FW-5 in