Protective Elements
Reconnection Module
Available Elements:
ReCon[1] ,ReCon[2]
The reconnection function after a mains decoupling is based on the requirements of the VDE AR-N 4120
1
and the
German directive „Erzeugungsanlagen am MS-Netz“
2
.
To monitor the reconnection conditions after a mains decoupling, a reconnection function has been implemented in
parallel to the decoupling functions.
Mains voltage (phase to phase) and frequency are the main criteria for reconnection. Always the mains side voltage
(line to line) at the generator circuit breaker (mains side) has to be evaluated.
The reconnection function is only one of the system functions for mains decoupling and return synchronizing.
The reconnection element is tied to decoupling functions like the
Q->&V<
element and other integrated decoupling
functions like under-/overvoltage, under-/overfrequency. The reconnection can be triggered by up to 6 decoupling
elements or via digital input signals, logic functions or via SCADA (communication system).
After a trip of the circuit breaker at the PCC by the decoupling function, reconnection has to be done manually.
Danger of an asynchronous reconnection:
The reconnection function does not substitute a synchronizing device.
Before connecting different electrical networks, synchronism has to be secured.
After decoupling by the
Q->&V<
module or other decoupling functions, like
V</V<<, V>/>>, f</>
the reconnection
release signal for reconnection the circuit breaker of the power generating unit will be blocked for a preset time
interval (default setting 10 minutes). This is to wait until all switching operations are completed. The automatic
reconnection must not be executed before mains voltage and frequency are inside the acceptable bands (quasi
permanent) that means within the admissible limit values for a preset, settable time.
The purpose of the reconnection function is to reconnect a decoupled energy resource safe to the mains/grid.
Release logic for the Generator Circuit Breaker
If the PCC circuit breaker has tripped the reconnection has to be done manually. A special blocking logic is not
necessary.
If a power generating unit should be reconnected by the generator circuit breaker the
voltage transformers have to be installed at the mains side of the circuit breaker.
1 „Technische Anschlussregeln für die Hochspannung“ (VDE-AR-N 4120)
2 Technische Richtlinie „Erzeugungsanlagen am Mittelspannungsnetz“, Richtlinie für Anschluss und
Parallelbetrieb von Erzeugungsanlagen am Mittelspannungsnetz, Ausgabe Juni 2008, BDEW Bundesverband der
Energie- und Wasserwirtschaft e.V., → see „3.2.3.2 – Blindleistungs-Unterspannungsschutz Q->&U<“ therein.
969 MCDGV4 DOK-HB-MCDGV4-2E
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