Basler Electric BE1-59N - Manual (Page 10)

Ungrounded Systems
The BE1-59N Ground Fault Overvoltage Relay is used to detect ground faults on ungrounded three-
phase-three-wire systems. The relay is connected as shown in Figure 1-1 . A set of voltage transformers
are wired with a grounded wye primary and a broken delta secondary. The BEl-59N is connected across
the broken delta. It is often necessary to connect a resistor across the broken delta to avoid
ferroresonance.
Grounded wye/broken delta voltage transformers act as a zero sequence filters by summing the three
phase voltages. Under normal conditions, this sum is zero. When a ground fault occurs, the BE1-59N
Ground Fault Overvoltage Relay will detect the presence of the secondary zero sequence voltage (3V
O
).
The BE1-59N Ground Fault Overvoltage Relay greatly reduces the risk of equipment damage by
detecting and isolating the first ground on an ungrounded system.
Figure 1-1. Ungrounded 3-Phase, 3-Wire System
MODEL AND STYLE NUMBER
BE1-59N electrical characteristics and operational features are defined by a combination of letters and
numbers that make up the style number. Model number BE1-59N designates the relay as a Basler
Electric Ground Fault Overvoltage Protective Relay. The model number, together with the style number,
describes the options included in a specific device and appears on the front panel, draw-out cradle, and
inside the case assembly.
The style number identification chart for the BE1-59N relay is illustrated in Figure 1-2.
1-2 BE1-59N General Information 9171400990 Rev K