Basler Electric BE1-32R - Manual (Page 29)

SECTION 3 • FUNCTIONAL DESCRIPTION
INTRODUCTION
BE1-32R and BE1-32O/U relay functions are illustrated in Figure 3-1 and described in the following
paragraphs.
Figure 3-1. Function Block Diagram
Current Sensing
System current transformers (CTs), with 5 Aac (nominal) secondary windings, supply the relay current
sensing transformers with current. For current sensing input ratings, refer to Section 1, General
Information, Specifications.
Sensing Input Range 1, 4, and 7 Current Rating
In some applications, the 7 ampere current rating for sensing input ranges 1, 4, and 7 may be exceeded if
due care is not exercised. The most common CT has a thermal rating factor of 1.33, yielding a maximum
continuous current of 6.67 amperes, which is below the rating of the relay. However, many CTs have
thermal rating factors of 1.5 or 2. In many applications, current that exceeds the rating of the relay might
be applied. The designer/engineer needs to recognize this relay limitation when setting up the steady-
state current that the relay is exposed to.
Sensing Input Range 1, 4, and 7 Burden
The burden for sensing input ranges 1, 4, and 7 can be high and have a substantial impact on the total
CT burden calculations and CT performance during fault conditions. The high burden can be easily
accounted for in normal operation and CT selection. However, the larger concern is what occurs during
fault conditions and how other relays on the CT string will be affected by the BE1-32 burden.
Phase Rotation Sensitivity
Relays that use phase current and phase-to-phase voltages to determine direction are sensitive to phase
rotation. BE1-32 Directional Power Relays with sensing type B, E, or V are phase rotation sensitive.
Unless otherwise noted, all connections shown in this manual assume ABC rotation.
9171100990 Rev T BE1-32R, BE1-32O/U Functional Description 3-1