Hitachi Relion 670 Series Applications Manual page 80

Section 6
Differential protection
ROA: Relay operate angle for zero sequence directional feature. It is used to differentiate an internal
fault and an external fault based on measured zero sequence current and neutral current. When the
winding is grounded via neutral point resistor, increase the ROA value to 115 degrees. Default value
of 60 deg is recommended.
6.2 Single-phase railway power transformer differential
protection T1PPDIF
6.2.1 Function revision history
Document
revision
A
B
C
D
E
F
G
H
J
M
N
6.2.2 Identification
Function description
Single-phase railway power transformer
differential protection
6.2.3 Application
The railway transformer differential protection is a unit protection. The function is designed to operate
properly for 16.7Hz, 50Hz and 60Hz railway power transformers. It serves as the main protection of
railway power transformers in case of winding failure. Internal electrical faults are very serious and
will cause immediate damage. Short circuits and earth faults in windings and terminals will normally
be detected by the differential protection. It is possible to detect inter-turn faults if a sufficient number
of turns is short-circuited. Inter-turn faults are the most difficult transformer winding fault to detect
with electrical protections.
It is important that the faulty power transformer can be disconnected as fast as possible. As the
differential protection is a unit protection, it can be designed for fast tripping, thus providing selective
disconnection of the faulty railway power transformer. The differential protection should never
operate on faults outside the protective zone. A transformer differential protection compares the
current flowing into the transformer with the current leaving the transformer.
74
Product History
revision
2.2.1 -
2.2.1 -
2.2.2 -
2.2.3 Waveform check made to depend on the level of the fundamental differential current.
2.2.3 -
2.2.3 -
2.2.4 -
2.2.4 -
2.2.5 -
2.2.6 -
2.2.6 -
IEC 61850
identification
T1PPDIF
© 2017 - 2023 Hitachi Energy. All rights reserved
GUID-388AD26B-6803-4C8B-9DE4-E90D0826EB30 v2
GUID-A2277232-DD35-4EF2-858A-AA666A467A2B v3
GUID-855CD002-4259-44F3-A491-E7DD119C6525 v2
IEC 60617 ANSI/IEEE C37.2
identification device number
87T
Id/I>
IEC15000166 V1 EN-US
GUID-147FA067-0F83-43E8-94B3-8EFFAD690AA3 v1
GUID-2986FDC3-BDBE-4741-9956-6AD89EFAD144 v1
Railway application RER670
1MRK506375-UEN Rev. N
Application manual