Installation/operation instructions ADL-111Q96/xxVDC
Page 5 of 7
4189330017B (UK)
Configuration of the max. leakage capacitor (stray earth capacitance)
Normally, the leakage capacitor is a phenomenon based on the cables in the IT power
network. When the cables are mounted close to the metal structure, e.g. the hull of
the ship, a capacitive coupling is unavoidable. The size of the capacitor can be
measured using insulation test equipment based on a known frequency and a known
test voltage.
If only the cables contribute to the leakage capacitance, the capacitance will be low -
less than 1
μ
F. On the other hand, the leakage capacitance can be higher, if the loads
connected to the power system are equipped with decoupling capacitors, e.g.
electronic equipment. To prevent incorrect insulation monitoring, set the ADL to
accept max. 20
μ
F capacitance, using the S1 switch.
Measuring ranges
The ADL-111Q96/xxVDC can be delivered with 3 different scale ranges dependent on
the voltage level on the IT power network: 50…0k, 250…0k or 500…0k for IT
networks with 24V DC, 110V DC or 220V DC respectively.
Scale range 50…0k
Ri 12k
If the setting on S1 is changed from 1
μ
F to 20
μ
F or vice versa, a
power-up reset is needed before the new setting is accepted. Power-up
reset is performed by disconnecting and reconnecting the aux. supply
(X1 or X2).
The ADL-111Q96/xxVDC is using a pulsating DC voltage connected to
the IT network through a known resistor. The reference of this known
resistor is Ri, and the value is printed on the scale.
