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ABB Power Grids Ltd.
Capacity C1 depends on the bushing temperature and increases by approximately 0.04% with an increase
in temperature of 1 ° C. The value of the capacity C1, related to 20 ° C:
С
= С
1,20°С
1 measured.*
10.3 Measuring equipment
10.3.1 Measuring bridge
To measure capacitance and tangents delta, use a measuring bridge (Schering bridge).
Examples of measuring bridges:
Table 4
Manufacturer
Doble Engineering Company, USA
Tettex Instruments, Switzerland
Tettex Instruments, Switzerland
Tettex Instruments, Switzerland
FGUP "NIIEMP", Penza, Russia
OOO NPO "Technoservice Electro", Moscow,
Russia
GNPP "Spetsavtomatika, Kiev, Ukraine
GNPP "Spetsavtomatika, Kiev, Ukraine
For the use of bridges, see the manufacturer's operation manual.
10.3.2 Power source
For measuring the capacitance and tgδ
or embedded in the measuring equipment.
10.4
Installation and connection of the bridge
Make sure that the transformer is off and out of service.
For safe and reduce influence of interference, short circuit all the transformer winding. Ground the winding
that are not connected to the bushing being tested.
Connect the measuring bridge to the test tap as required in the relevant operation manual.
Depending on which insulator is checked, connect the power source (test voltage) to the terminate plate or
the test tap.
Testing wires must be as short as possible and must not contact grounded objects.
The test tap must be clean and dry.
10.5
Measurement procedure
Connect the grounding terminal of the bridge to the transformer grounding terminal. The flange of the
bushing not installed on the transformer and to be measured must be grounded.
Before putting the bushing into service, carry out a measurement of dissipation factor tgδ
at the voltage up to 10 kV in order to have a reference for later checks.
On completion of measuring, remove the test adapter from the test tap and screw on the protective cover to
protect the test tap from moisture and contamination (in this case the test tap is grounded automatically).
The test tap must not be open during service or storage.
12
(1 – ΔТ
0,0004), where ΔТ = Т
*
use at least a 10 kV power source. The source may be independent
1
GKSL 680205.021 RE
Rev. 2, 26.09.2019
– 20°С
bushing
Model
M2H
2809
2816a
2820
Tangens 2000
Vektor-2.0 M
P-5026 M
CA7100-1, CA7100-2
and capacity C
1
1
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