Biased Differential (87Bd, 87Hs) - Siemens 7SR18 Solkor Manual

7SR18 Commissioning & Maintenance Guide
2.1
B D
IASED
Current Inputs:
Disable:
Map Pickup LED:
The differential elements are subjected to CT multipliers, Vector Group Compensation and Zero Sequence filters
when applied to power transformers. The complexity of these features can cause confusion during testing and
lead to incorrect relay settings being applied. It is recommended that the accuracy of the differential elements are
tested by secondary injection with simplified differential settings applied to avoid ambiguity before reinstating the
required site settings which can be tested more thoroughly by primary injection followed by final checking with the
protected transformer on load.
Unrestricted Page 12 of 54
(87BD, 87HS)
IFFERENTIAL
Ia Ia Ia Ia
Line Prim Sec Nom.
Ib Ib Ib Ib
Line Prim Sec Nom.
Ic Ic Ic Ic
Line Prim Sec Nom.
I
I EF
Seq.
Der.
Comp
Meas
Earth
Meas
Earth
I
I EF
Seq.
Der.
Comp
Ic Ic Ic Ic
Line prim sec Nom.
Ib Ib Ib Ib
Line prim sec Nom.
Ia Ia Ia Ia
Line prim sec Nom.
Figure 2.1-1 Biased Differential
I I , I ,
A, B C
46, 49, 50, 51, 50N, 51N, 50BF,
87BD, 87HS - Self Reset
nd
2
Therm
Harm
nd
2
Therm
Harm
nd
2
Therm
Harm
Local
Loc Loc Loc
Rel. Rel. Rel.
Ic Ib Ia
Ia
Op.
Ib
Op.
Ic
Op.
Rmt Rmt Rmt
Rel. Rel. Rel.
Ic Ib Ia
Remote
nd
2
Therm
Harm
nd
2
Therm
Harm
nd
2
Therm
Harm
©2018 Siemens Protection Devices Limited
Local
Relay
Ia
Rest.
Ib
Rest.
Ic
Rest.
Remote
Relay