3.8.3 Functional diagrams
The functional diagrams describe the default input, output, alarm LED and function-
to-function connections. The default connections can be viewed with SMT and
changed according to the application requirements.
The analog channels, measurements from CTs and VTs, have fixed connections
towards the different function blocks inside the IED’s standard configuration.
Exceptions to this rule are the 12 analog channels available for the disturbance
recorder function. These channels are freely selectable and a part of the disturbance
recorder’s parameter settings, thus not included in the SMT functionality.
The analog channels are assigned to different functions as shown in the functional
diagrams. The common signal marked with 3I represents the three phase currents and
3U the three phase voltages. The signal marked with I
0
represents the measured
residual current via a core balance CT. The signal marked with U
0
represents the
measured residual voltage via open delta connected VTs.
The EFHPTOC protection function block for double (cross-country) earth faults uses
the calculated residual current originating from the measured phase currents.
3.8.3.1 Functional diagrams for protection
The following functional diagrams describe the IED’s protection functionality in
detail and according to the factory set default connections in SMT.
Four overcurrent stages are available for overcurrent and short-circuit protection.
Three of them include directional functionality (DPHxPDOC). The non-directional
instantaneous stage (PHIPTOC1) can be blocked by energizing the binary input 1
(X120:1-2). Two negative-sequence overcurrent stages (NSPTOC1 and NSPTOC2)
are available for phase unbalance protection. The inrush detection block’s
(INRPHAR1) output BLK2H enables either blocking the function or multiplying the
active settings for any of the shown protection function blocks.
Section 3 1MRS756378 D
REF615 variants
96 REF615
Application Manual
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