ABB Relion 670 series, Technical Reference Manual

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11.2.1 Introduction
The aim of the fuse failure supervision function (SDDRFUF) is to block voltage
measuring functions at failures in the secondary circuits between the voltage
transformer and the IED in order to avoid unwanted operations that otherwise might
occur.
The fuse failure supervision function basically has three different algorithms, negative
sequence and zero sequence based algorithms and an additional delta voltage and delta
current algorithm.
The negative sequence detection algorithm is recommended for IEDs used in isolated
or high-impedance grounded networks. It is based on the negative-sequence measuring
quantities, a high value of voltage without the presence of the negative-sequence
current 3I
2
.
The zero sequence detection algorithm is recommended for IEDs used in directly or
low impedance grounded networks. It is based on the zero sequence measuring
quantities, a high value of voltage 3V
0
without the presence of the residual current 3I
0
.
For better adaptation to system requirements, an operation mode setting has been
introduced which makes it possible to select the operating conditions for negative
sequence and zero sequence based function. The selection of different operation modes
makes it possible to choose different interaction possibilities between the negative
sequence and zero sequence based algorithm.
A criterion based on delta current and delta voltage measurements can be added to the
fuse failure supervision function in order to detect a three phase fuse failure, which in
practice is more associated with voltage transformer switching during station operations.
11.2.2 Principle of operation
11.2.2.1 Zero and negative sequence detection
The zero and negative sequence function continuously measures the currents and
voltages in all three phases and calculates, see figure
303 :
• the zero-sequence voltage 3V0
• the zero-sequence current 3I0
• the negative sequence current 3I2
• the negative sequence voltage 3V2
The measured signals are compared with their respective set values 3V0PU and 3I0PU ,
3V2PU and 3I2PU .
1MRK505222-UUS C
Section 11
Secondary system supervision
601
Technical reference manual