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the basis of the above criterion, field trial of the Figure 4: PD Map as a Function of Time (Z Axis) along the
following 33kV sections done at site. length of the cable (X Axis). The PD intensity is plotted against
the vertical Y axis
Table 1: Cable PD located by Online Pinpointing Techniques
Sl. No. Suspected 33 kV Cable Sections This problem is solved by using at least two sensors
1 Botanical GIS – Belilious Park GIS located at both ends of the cable and by doing periodic
2 Bally GIS - Belur GIS and synchronized captures. After each capture, the
3 KRS - Ritchie GIS F2 electrical background noise is removed and the time
4 Princep St GIS - Kidderpore GIS F2 delay of the same partial discharge signal to the two
5 BBD Bag GIS - Strand South GIS sensors placed at the ends of the cable to identify the
6 KRS - New Ballygunge (E) D/S T3 actual location of the partial discharge source. This
method can only be applied effectively by prior removal
Table 2: Cable PD located by Spot Measurement Techniques of the background noise signals to observe the captured
Sl. No. Suspected 33kV Cable Sections partial discharges clearly.
1 BT Road - Sinthia North GIS
2 EMSS GIS - KRS Siemens Board Identification and separation of Di erent
3 EMSS - Panditiya GIS Partial Discharge Sources
4 Sinthia GIS - Tallah DS 33kV RMU
Efficiency of the conventional methods for identifying and
SPOT MEASUREMENT PHILOSOPHY separating different partial discharge sources is limited
by the uncertainty in the location of the PD source. For
Automatic Partial Discharge location in example, the uncertainty in the partial discharge location
Insulated Cables along a cable is few meters, so it is possible to have one
or more partial discharge sources in the same location,
The majority of the procedures used in the market treat especially in the open ends of the cables where they can
the location of partial discharge sources by the technique appear corona PDs and outer surface PD.
of reflectometry, which consists of acquiring signals at a
measuring station placed at one end of the cable and Identification of the PD source type is unsolved in most
determine the time delay between the signal coming of the cable insulation diagnostic techniques, leaving
directly from the partial discharge source and the signal this decision to the discretion of the operator. Some
coming from the reflection at the opposite end of the techniques use the phase shift of the partial discharge
cable where the circuit is left open. with respect to the applied voltage to generate a phase
resolved pattern of the detected PD sources in order to
The position of the partial discharge source along the assist the operator in making the decision, but as already
cable is also determined by taking into account the indicated, patterns are produced.
propagation speed of the partial discharge signal through
the cable. The practical limitation of this technique for “on
line” measurement is that one end of the line must be
open so that the PD signal could reflect, which prevents
it to be applied in actual operating conditions.
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following 33kV sections done at site. length of the cable (X Axis). The PD intensity is plotted against
the vertical Y axis
Table 1: Cable PD located by Online Pinpointing Techniques
Sl. No. Suspected 33 kV Cable Sections This problem is solved by using at least two sensors
1 Botanical GIS – Belilious Park GIS located at both ends of the cable and by doing periodic
2 Bally GIS - Belur GIS and synchronized captures. After each capture, the
3 KRS - Ritchie GIS F2 electrical background noise is removed and the time
4 Princep St GIS - Kidderpore GIS F2 delay of the same partial discharge signal to the two
5 BBD Bag GIS - Strand South GIS sensors placed at the ends of the cable to identify the
6 KRS - New Ballygunge (E) D/S T3 actual location of the partial discharge source. This
method can only be applied effectively by prior removal
Table 2: Cable PD located by Spot Measurement Techniques of the background noise signals to observe the captured
Sl. No. Suspected 33kV Cable Sections partial discharges clearly.
1 BT Road - Sinthia North GIS
2 EMSS GIS - KRS Siemens Board Identification and separation of Di erent
3 EMSS - Panditiya GIS Partial Discharge Sources
4 Sinthia GIS - Tallah DS 33kV RMU
Efficiency of the conventional methods for identifying and
SPOT MEASUREMENT PHILOSOPHY separating different partial discharge sources is limited
by the uncertainty in the location of the PD source. For
Automatic Partial Discharge location in example, the uncertainty in the partial discharge location
Insulated Cables along a cable is few meters, so it is possible to have one
or more partial discharge sources in the same location,
The majority of the procedures used in the market treat especially in the open ends of the cables where they can
the location of partial discharge sources by the technique appear corona PDs and outer surface PD.
of reflectometry, which consists of acquiring signals at a
measuring station placed at one end of the cable and Identification of the PD source type is unsolved in most
determine the time delay between the signal coming of the cable insulation diagnostic techniques, leaving
directly from the partial discharge source and the signal this decision to the discretion of the operator. Some
coming from the reflection at the opposite end of the techniques use the phase shift of the partial discharge
cable where the circuit is left open. with respect to the applied voltage to generate a phase
resolved pattern of the detected PD sources in order to
The position of the partial discharge source along the assist the operator in making the decision, but as already
cable is also determined by taking into account the indicated, patterns are produced.
propagation speed of the partial discharge signal through
the cable. The practical limitation of this technique for “on
line” measurement is that one end of the line must be
open so that the PD signal could reflect, which prevents
it to be applied in actual operating conditions.
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