Voltage Sensors; Supervision; Table 3: Voltage Metering Accuracy; Table 4: Zero-Clamping Limits - ABB UniGear Digital Commissioning And Testing Manual

PR IM AR Y T ES T IN G
4.3

Voltage sensors

Primary testing verifies the whole measurement chain including the sensor, cable connec-
tions and settings of the protection relay. Physical polarity of the voltage sensor is unique,
only one-way installation is possible. Therefore, no polarity (physical test) is needed.
4.3.1

Supervision

In the protection relay, voltage metering is supervised by the VMMXU function. Metering ac-
curacy is stated in Table 3.

Table 3: Voltage metering accuracy

Characteristic
Operation accuracy
A measured value under the zero-point clamping limit is forced to zero. This allows the noise
in the input signal to be ignored. Read more details in the technical manual of the protection
relay.

Table 4: Zero-clamping limits

Function
Three-phase voltage measurement (VMMXU) 1% of nominal (Un)
Residual voltage measurement (RESVMMXU)
Phase sequence voltage meas. (VSMSQI)
1 VLG 500 0 17 C
Value
• Depending on the frequency of the
measured voltage: f
• ±0.5% or ±0.002 × U
range 0.01-1.15 × U
Zero-clamping limit
1% of nominal (Un)
1% of the nominal (Un)
VO LTAG E SE NSO R S
±2 Hz
n
(at voltages in
n
)
n
2 9