After the french standard NFC 18311, the IEC also established a standard based on the laboratory research of the European standard (NFC, VDE).
FAMECA had to retain their lead by designing detectors that comply both with the IEC standard and comprehensive field configurations.
Use of voltage detectors
Voltage detectors are mainly used to check the absence of voltage before earthing a circuit. This device must therefore indicate whether or not nominal voltage is present.
Previous detectors with wide range detection or proximity detection required a sound knowledge of the network to determine the presence of nominal or induction.
Electronic voltage detectors using a direct contact measurement and an adapted threshold, provide a simple and safe indication.
- Threshold value: detection of nominal voltage above any induced voltage that could appear
- Direct contact: reduces the influence of electrical disturbance (double circuit or substation)
How to choose a voltage detector
- Low disturbance area : a wide range voltage detector can be used.
The threshold value is selected as follows :
Ut = threshold voltage
U min = lowest voltage of the range
U max = highest voltage of the range
Threshold limits 0.1 U max < Ut < 0.45 U min
Example : Range = 11 kV to 33 kV
Threshold limits 3.3 kV < Ut < 4.95 kV
Threshold Ut ≈4.1 kV
- High disturbance area (on double circuit overhead line or substation)
In some specific cases the induced voltage level and strong electrical interference require a higher threshold voltage.
In this case the IEC standard allows a voltage detector with a narrow range or even single voltage, to improve the resolution :
Threshold limits 0.15 Umax < Ut < 0.40 Umin
Example : Range = 33 kV
Threshold limits 4.95 < Ut< 13.2
Threshold Ut = 9 k
