A Background to Low Voltage (LV) Current Transformer (CT) Testing

The Australian Energy Market Operator (AEMO) National Electricity Market (NEM) Rules (specifically chapter 7 relating to metering equipment) contain the approach that is required with respect to the management of metering assets. A business can submit, and if successful obtain, AEMO approval to implement alternative testing/inspection/maintenance approaches with respect to its metering assets and part of its wider Metering Asset Management Plan (MAMP).

The traditional pricing of MP/MDP services from metering businesses exclude the ongoing maintenance and testing of the VT and/or CT assets as these assets are not theirs to maintain “fit for purpose”. The costs associated with the compliance for maintenance of the VT’s and or CT’s is a matter for the Responsible Person (generally the Retailer) and for to determine its strategy on how to recover or minimise these costs to its business.

The NER’s dictate 100% testing of CT’s every 10 years which in summary means that 10% of NEM CT’s are required to be tested every year. Testing of HV VT/CT assets has somewhat been addressed but these sites tend to be very large and have small windows of opportunity to get them off-line to carry out the required tests. LV CT categories remained untouched.

A number of issues remained unclear in the first 10 years of the market and these included the following:

  1. The age of the assets
  2. The ownership of the assets
  3. The responsibility of maintaining/testing of the assets
  4. The accountability of paying for maintaining/testing of the assets
  5. The avoidance of trying to organise an outage
  6. The absence of an effective secondary injection methodology to minimise the testing time and costs

In 2011 and mid 2012 AEMO have pushed the market participants and have placed the accountability on the RP’s to make LV CT testing happen and address or overcome some of these issues and through the CT working group challenged the current rules and the outcome was the creation of the “Alternative Testing Minimum Requirements: Low voltage Current Transformer metering Installations”. AEMO_-_Alternate_Testing_Minimum Requirements_LV_CTs_V1.1

RP’s have had the choice from May 2012 of 10% testing or the Alternative Testing (Sampling approach) and it Retailers have decided to carry out one or the other.

Compliance Bulletin
The Australian Energy Regulator issued a compliance Bulletin No.6 in December 2011 and AEMO is required to administer this with direction given to the Retailers (Responsible Person) with Rule Enforcement. Compliance Bulletin No 6 – Testing requirement for instrument transformers

Metering Dynamics Resource Capability for Carrying out LV CT Tests & ESI’s
Metering Dynamics have been carrying out LV CT Tests and Enhanced Sites Inspection (ESI’s) as directed by RP’s on behalf of its Retailers for the past 2 years and will be required to continue to carry out this work indefinitely. Metering Dynamics invoice the RP for the services that they have requested. This has amounted to 1000’s of tests and 1000’s of ESI’s