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2 Functions
176
7ST6 Manual
E50417-G1176-C251-A3
Figure 2-55
Manual closing with external automatic reclosure device
CB
Circuit breaker
ON
Circuit breaker close coil
CBaux
Circuit breaker auxiliary contact
Depending on the configuration of the distance protection, an undelayed trip
command can be generated after energisation for each pickup or for pickup in . The
line energisation recognition function is also used by the stages of the overcurrent pro-
tection.
Blocking of Under-
voltage Protection
In configurations with voltage transformers on the line-side and single-side infeed, no
voltage is measured after tripping of the line. If activated, the undervoltage protection
would in such a case cause a spurious trip. In this condition it would no longer be pos-
sible to energize the line, since the presence of a TRIP command from the undervolt-
age protection would prevent energization.
To identify such situations, 7ST6 devices are provided with a residual current detection
which blocks the undervoltage protection if the currents drop below a specified thresh-
old of 0.05 I
n
. As soon as a significant current level (I>0.05 I
n
) is measured on the line,
the line is assumed to be energized, and the blocking is reset.
2.18.1.2 Detection of the Circuit Breaker Position
For Protection Pur-
poses
Several protection and auxiliary functions require information on the status of the
circuit breaker for proper functioning. This is, for example, of assistance for
• The automatic reclosure (refer to Section 2.12),
• The It (refer to Section 2.15)
The device is provided with the signals for detection of the circuit breaker auxiliary con-
tacts. The above functions assumes the circuit breaker auxiliary contacts to be wired
if these signals have been configured to binary inputs. Therefore, signals for non-wired
feedback information must not be configured to a binary input.
For Trip Circuit Su-
pervision and
Switch Objects
For these functions separate binary inputs with information on the circuit breaker po-
sition are available.
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