Analysis of HV Faults8/19 September 1999
(based on NAFIRS data available 11.10.99)
1. Analysis by Network Voltage
Hours Lost (CHL)
|33 kV||9 (14%)||5,282 (29%)||9,101 (16%)|
Note: 11 kV60 NAFIRS entries (including
4 "supply infeed failures to neighbouring districts"
and 2 "extension of fault zone" entries)54
separate faults excluding above duplicates.
2. 11 kV FaultsAnalysis by degree of
|Category|| ||Data for 18-19 September 1999|
| ||Population (km)||Circuits||Faults||Faults per 1000 km**||CI||CHL|
Complete* includes those circuits that have been
completely refurbished but part of which wascarried out
to the pre-95 specification.
Faults per 1000 km**No. of faults normalised against circuit
length in population.
3. 11 kV FaultsAnalysis by cause and
| ||None||Partial||Complete||Complete*|| |
Note: Faults attributed to "trees"
includes both those assigned as either Direct or Contributory
Cause in NAFIRS.
In assessing the performance of refurbished circuits
the following points should be borne in mind:
obvious dangers in basing definitive conclusions on a relatively
small sample size.
this caveat, the analysis does suggest that those circuits that
have been completely refurbished performed significantly better.
that have been partially refurbished performed worse than those
with no refurbishment. This is because inherently, the circuits
on which work is in progress are rogue circuits which by their
nature are the worst performing. In addition, this also demonstrates
that the benefits of refurbishment do not become apparent until
the circuit is completed.