C OMMENTS O N B ENCHMARKING A ND C OMPARATIVE R EPORTING

Measurement data is not available for individual sites: this section discusses statistics for complete transmission or distribution systems.

Where significant international performance statistics are available for Distribution companies (primar- ily through company annual reports and the work of organizations such as the IEEE [35] in the US, the CEA in Canada [42], and the CEER [45] in Europe), sources of comparative transmission performance statistics are very limited. Where differences in the specific definitions of indices are a major concern in the case comparisons of Distribution companies, Transmission companies often use very different combinations of indices. These are also often applied differently.

Possibly the most consistent transmission system interruption performance study being undertaken from a benchmarking perspective is that of the Canadian Electricity Association (CEA) in Canada. Fourteen utilities are involved in the study, and 5-year performance reports are generated annually.

These are available to members only (the CEA on the other hand makes the results of a similar distri- bution performance study available public). The only significant transmission performance surveys re- ported on by Cigre and UNIPEDE are [46] and [30]. EPRI has undertaken a transmission reliability benchmark study, but this was based on probabilistic techniques (similar to those applied by the vari- ous reliability councils in the USA), and did not address actual interruption performance.

International recommendations in 1999 by Cigre WG 39.04 on measurements of quality in transmis- sion systems are that SAIFI, SAIDI, and SAIRI be used as interruption performance indicators. The specific definition of these is interesting in that they apply to delivery and reception points (generators and inter-connectors) [30]. Despite this Cigre WG 39 recommendation, actual practice indicates that different transmission companies in Europe and Australia use or are proposing to use other sets of reporting parameters. These indices are however used extensively in Canada (through the co- ordination of the CEA project).

Significant efforts to develop more appropriate quality and continuity measurement methods for a competitive industry are being driven by both regulators and utilities. This is evidenced by the large number of information sources (published over the last 3 years) that are listed as reference material in this report. Interruption performance reporting is seen as a component of other reporting requirements for future transmission grids. Additional components include availability, and system constraints [47], [29]. In many cases, incentives are in place or are being considered.

A conclusion on inter-utility benchmarking formulated by the IEEE/PES working group on system de- sign is that performance "cannot be compared between companies by simply comparing indi- ces…many other factors must be taken into consideration" [48]. A similar conclusion was reached this year in an Australian attempt at international transmission system benchmarking, i.e. the Australian experience is that these problems make "inter-company and international comparisons difficult if not impossible" [47].

The benchmarking of transmission performance is complicated by the combination of unique influenc- ing factors in each country (geography, environmental conditions, load density, the location of genera- tion sources, the degree of excess capacity, network topology, system voltage levels). The dominant benchmarking approach for Transmission companies is therefore based on historical performance of the company itself. This is evident in various countries such as the UK's (OFGEM’s work related to the BETTA project - which acknowledges the need for "geographic" differentiation in its proposed stan- dards), Australia (ACCC's project to benchmark each of its transmission companies by the end of the year, based on the last 5 years of data for each utility), New Zealand (TransPower's specific differen- tiation of planned and unplanned system minutes due to the radial nature of its system). The focus of the CEA study is difficult to assess because of the propriety nature of the information.

Company Interruption measures Target Actual Performance

/ Organisation 1999 2000 2001

Company 1 Circuit availability 99% 99.6286%

Circuit services availability 99.999% 99.9992%

System minutes (Transmission Code) 5 5

System minutes (Conventional) - -

Number of supply interruptions 21 27

Company 2 Total number of unplanned interruptions 110 62 102

(mandatory) Total system minutes (all interruptions) 9.7 4.9 12.4

- system minutes (planned) 2.7 2.8 0.9

- system minutes (unplanned) 7.1 2.1 11.6

Underlying system minutes (<= 1 system minute) 7.3 4.9 4

- system minutes (planned) 1.7 2.8 0.9

- system minutes (unplanned) 5.6 2.1 3.1

Average supply reliability (%) 99.9972 99.9986 99.9963

Planned interruption restoration performance 94.4 100.0 89.5

Unplanned interruption response (%) 100 100 100

Company 2 Availability (AC system) 98.7% 99.2%

(additional) Availability (HVDC system Bipole 1) 95.0% 97.3%

Availability (HVDC system Pole 1) 92.5% 95.8%

Availability (HVDC system Pole 2) 97.7% 98.9%

Average number of interruptions per supply point 0.39 Every supply point - number of events n/a specified per point

Company 3 Average interruption time (AIT) n/a n/a

Company 4 Number of incidents 3

Average incident duration 68min

Average Unsupplied Energy Per Incident 292 MWh

Interconnector A availability 96.2%

Interconnector B availability 99.7%

Average annual system availability 95.8%

Company 5 SAIFI-SI (> 1 minute events) n/a

SAIFI-MI (< 1 minute events) n/a

SAIDI n/a

SARI n/a

Company 6 SAIFI-SI n/a n/a

SAIFI-MI n/a n/a

SAIDI n/a n/a

SARI n/a n/a

DPUI n/a n/a

Company 7 No. of interruptions (planned, unplanned, incl < 1 min) n/a n/a

CI (planned, unplanned, incl < 1 min) 0.65 hrs/yr n/a

SAIFI n/a n/a

MAIFI n/a n/a

System Minutes (previous year peak demand) n/a n/a

Company 8 Number of interruptions over last 3 years 3

Total hours interrupted over last 3 years 9 hrs

Company 9 Load not served (minutes) n/a 7.4 6

Customer connection point interruptions (frequency) n/a 1.25 1.17

Company 10 SAIDI 23.6

TSMAIFI (100kV) 2/year

TSMAIFI (44kV) 4/year

Company 11 System minutes 50

Number of interruptions

Company 12 System minutes

Number of interruptions SAIDI

CAIDI

Regulator 1 Circuit availability to be based on 5 yrs data

(proposal 2002) Minutes off supply to be based on 5 yrs data

Average restoration time to be based on 5 yrs data Hours constrained (intra-region) to be based on 5 yrs data Hours constrained (inter-region) to be based on 5 yrs data

Regulator 2 Number of incidents 3 - 10

Average Unsupplied Energy Per Incident 2 - 292 MWh

Unavailability (monthly basis) 0.5% - 7.5%

Regulator 3 Interruption cost mechanism utility to decide on spending new for 2002

Number of interruptions Energy not supplied

CEA Survey SAIFI (all interruption - including < 1 min) n/a available to participants only

(14 participants) SAIDI (all interruption - including < 1 min) n/a available to participants only System Minutes (previous year peak demand used)* n/a available to participants only

SARI n/a available to participants only

Cigre 1999 SAIFI n/a n/a

SAIDI n/a n/a

SAIRI n/a n/a