150
Applications Guide
Test Procedure on a Multi-Unit Arrester Stack
Assemblies consisting of three units or more per phase are tested in the manner outlined in figure 53
on the next page. Again, the line is de-energized and grounded then disconnected from the arrester
stack.
DUT
Test
Mode
High
Voltage
to
INPUT
A
to
INPUT
HV GND
to
GND
S1
UST A
2
1
3 (or 5)
5 + 3
S2
GST gA+B
2
1
3 (or 5)
5 + 3
S3
GST gA+B
3
1
4 (or 5)
5 + 4
S4
GST gA+B
4
1
5
5
Multi unit arrester stack measurement, connection for measurement of S1.
14.8.3
Measuring Data Interpretation
Normally it is unnecessary to normalize the measurement result to a standard temperature since most
types of surge arresters show only very little temperature dependence. Nevertheless if there is a
substantial temperature influence it is useful to establish a temperature correction curve for each
arrester design.
Surface leakage must be taken into account when power losses are measured. It can usually be
minimized by wiping the porcelain with a plain, dry cloth. In some circumstances it might be necessary
to use cleaning agents and waxes or to heat the porcelain surface.
Power loss values should be compared to older measurements or to similar units located under same
conditions. If manufacturer data are available, they should be considered first.
Once a range of losses has been established, any deviation, either higher or lower, should be
investigated. The following table points out the most important causes if abnormal losses are obtained
and the surface leakage can be neglected.
Higher than Normal Losses
Contamination by moisture and/or dirt or dust deposits on the inside surfaces of the porcelain
housing, or on the outside surfaces of sealed-gap housings.
Corroded
gaps.
Deposits of aluminum salts apparently caused by the interaction between moisture and products
resulting from corona.
Cracked
porcelain.
Lower than Normal Losses
Broken shunting resistors.
Broken pre-ionising elements.
Mistake in assembly.
Poor contact and open circuits between elements.
Summary of Contents for MIDAS 2881
Page 6: ......
Page 10: ......
Page 64: ...54 Software...
Page 109: ...Accessories and Options 99 Schematics Overview of the 5289 inductor and it s shielding...
Page 119: ...Conformity 109 13 Conformity...
Page 120: ...110 Appendix Appendix...
Page 159: ...Applications Guide 149...
