Table of Contents
Advertisement
6
49.En_Trp
7
49.En_Alm
8
49.OutMap
3.5 Zero Sequence Overcurrent Protection
3.5.1 Definite Time Zero Sequence Overcurrent Protection
The zero sequence overcurrent protection in this relay provides two groups of zero sequence
overcurrent protections with independent definite time delay characteristics. Each stage can be
enabled or disabled independently by the corresponding logic setting respectively.
The No.1 group has six stages, and the first four stages can be controlled with the directional
element, harmonic blocking element respectively. The last two stages are pure zero sequence
overcurrent protections. The four stages of the No.2 group are same with the first four stages of
the No.1 group.
The zero sequence current of the No.1 group of zero sequence overcurrent protection can be
derived from a dedicated zero sequence current transformer or be self-calculated (through the
setting [Opt_3I0]), and the zero sequence current of the No.2 group of zero sequence overcurrent
protection only can be led from another dedicated zero sequence current transformer.
When this relay is used in non-effective grounding (such as the delta side of a transformer) or
small current grounding system, the grounding zero sequence current during earth fault is
basically small capacitive current. Correct selection of faulty phase in zero sequence prot ection
can not be ensured by detection of such a current. Since all protection equipments are connected
with each other via network and information resource can be shared in the substation automation
system, so the faulty feeder can be identified firstly by comparing information from various feeders
which are connected to the same busbar and then decided finally by trial tripping of the circuit
breaker of the selected feeder. In this case, the zero sequence current must be derived from a
zero sequence current transformer.
When this relay is used in small resistance grounding system, the grounding zero sequence
current during earth fault is larger and can be used for tripping directly. All stages are equipped for
the zero sequence overcurrent protection. In this case, the zero sequence current for tripping can
be calculated or directly derived from a zero sequence current transformer.
Here, take the No.1 group of zero sequence overcurrent protection as an example to explain the
operation theory of the zero sequence overcurrent protection. The operation theory of the No.2
group of zero sequence overcurrent protection can be gotten on the analogy of this. The following
figure shows the logic diagram of the No.1 group of zero sequence overcurrent protection.
PCS-9611 Feeder Relay
The logic s etting of the thermal overload
protection for tripping
The logic s etting of the thermal overload
protection for alarming
The output matrix setting of the thermal overload
protection
Date: 2014-04-08
3 Operation Theory
0~1
1
0~1
1
0x00000 ~
1
0xFFFFF
3-19
Advertisement
Chapters
Table of Contents
