Bender A-ISOMETER AGH575S-6, Руководство по эксплуатации

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Function
12 TGH1384en/06.2005
2.2 Product description
The A-ISOMETER® IRDH275BU-6 and coupling device AGH575S-6 monitor
the insulation resistance of IT medium voltage systems up to 3.6 kV. It is suit-
able for universal use in 3/(N) AC, AC/DC and DC systems. AC systems may
include extensive DC supplied loads, such as converters or thyristor-control-
led DC drives. Drive systems including a converter and a motor in medium
voltage systems can be monitored. When the AGH575S-6 is connected in the
mid-point of the converter DC intermediate circuit, a maximum of
± 3.6 kV
against PE may occur. The device automatically adapts itself to the existing
system leakage capacitance.
The IRDH275BU-6 can be used in combination with a control and indication
panel, e.g. PRC1470 version 2 or higher, on the BMS (BMS = Bender Meas-
uring Device Interface) bus.
2.3 Function
The combination A-ISOMETER® IRDH275BU-6 and coupling device
AGH575S-6 is operated between the unearthed system (IT system) and the
protective conductor (PE).
The response values and other function parameters are set via the function
keys. The parameters are indicated on the LC display and are stored in a non-
volatile memory (EEPROM) after the setting is completed.
A microprocessor-controlled pulsating AC measuring voltage is superim-
posed on the IT system to be monitored (
measuring principle*). The
measuring cycle consists of positive and negative pulses of the same ampli-
tude. The period of these pulses depends on the respective system leakage
capacitances and the insulation resistances of the IT system to be monitored.
An insulation fault between the IT system and earth closes the measuring cir-
cuit. From the measured current value, the microprocessor calculates the in-
sulation resistance which is indicated on the LC display or the external kOhm
measuring instrument.
The measuring time t
an
is determined by the system leakage capacitances,
the insulation resistance, and the system-related interference disturbances.
System leakage capacitances do not influence the measuring accuracy. When
virtually no disturbances are caused by the operation of converters, the
measuring process takes about five minutes.
If the reading is below the selected response values Alarm 1/Alarm 2, the as-
sociated alarm relays respond and the alarm LEDs "Alarm 1/2“ light up and