Summation Principle; Introduction - ABB REB670 Applications Manual

1MRK 505 337-UUS -
6.1.5
6.1.5.1
Application manual
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ANSI06000125 V1 EN
Figure 71: Combination between one-and-half breaker and double busbar station
layouts
For this type of busbar arrangement the double busbar bay is usually connected to the
reactive power compensation equipment (that is, shunt reactor or shunt capacitor). The
diameters in the one-and-half breaker part of the station have at the same time the role of
the bus-coupler bay. Therefore, zone interconnection, zone selection and disconnector
replica facilities have to be provided for all double busbar bays.

Summation principle

Introduction

A simplified bus differential protection for phase and ground faults can be obtained by
using a single, one-phase IED with external auxiliary summation current transformers. By
using this approach, more cost effective bus differential protection can be obtained. Such
a solution makes it feasible to apply bus differential protection even to medium voltage
substations. The principal differences between full, phase-segregated bus differential
protection scheme and summation type bus differential protection scheme are shown in
figure 72.
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Section 6
Differential protection
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