Three key benefits:
- Smart Cable Guard confirms Helen’s position as an innovative distribution network operator with excellent quality and security of supply
- Smart Cable Guard is a mature online monitoring platform, commercially available on the market
- Smart Cable Guard has proven its concept by meeting all expectations based on offline partial discharge measurements, and in the monitoring of long feeders
The customer
Helen Electricity Network is part of the Helen Group, which is owned by the City of Helsinki. Helen is Finland’s third-largest electricity distribution company and serves 400,000 customers in the capital with a 6,300 km distribution network, including a 20 and 10 kV medium-voltage network of 1,600 km. Currently, the medium-voltage network comprises 99.7% underground cables that supply the city’s peak demand of 830 MW. The power cable network is a mixture of older PILC and newer XLPE power cables.
Serving government offices and business headquarters as well as residential customers in Finland’s most populated city, Helen has to meet the highest levels in reliability and quality of supply. On average, a Helsinki resident has a power cut lasting 30 minutes only every ten years.
The challenge
In 2010 Helen realised that its network had started experiencing an increase in power cuts Helen initiated an internal study to map the situation and to get answers to the questions: “What is the condition of the current network?” and “will it get worse?”. The investigation on the health and condition of its medium-voltage cable network was to identify the fault causes and to initiate measures to avoid future blackouts. Specifically, Helen wanted to know more about the condition of the older PILC cables in its network. One of the successive actions from this study was that Helen started to perform offline partial discharge measurements on its old and new cables. As Helen is not only a top-level company in terms of security of supply, but also an innovative distribution system operator working at the front of new technological developments, it decided to involve the Technical University of Tampere to conduct research on online partial discharge measurement systems. That is where Smart Cable Guard was identified as a platform to perform online partial discharge monitoring of medium-voltage power cables.
Today, Helen has a highly automated network with fault indicators that act on short circuits and earth faults in the system, enabling it to switch off the cable and to re-route the power flow fast. Helen gains knowledge about Smart Cable Guard exploring future applications in a highly automated network. This means that Helen has an excellent quality and security of supply track record, a position it wants to maintain both in the near-term and in the future. A future target for Helen is to investigate possibilities to upgrade systems to serve its 110 kV network feeders.
DNV’s contribution
Offline partial discharge measurement is an effective tool for commissioning tests, but shows low benefit with cables that are already in service, because the cable has to be de-energized during the measurement. However, online partial discharge measurements enable real-time condition monitoring of in-use medium-voltage networks, providing valuable information for life-cycle planning. Smart Cable Guard is a very effective tool for online detection and location of (intermittent) faults and partial discharges in medium-voltage power cables. Helen started this online partial discharge measurement project, using DNVs measuring and monitoring platform Smart Cable Guard to compare and confirm identified weak spots in the network obtained by offline partial discharge measurements. As Helen had already identified the weak spots, Smart Cable Guard sensors were placed to monitor only those cables with the most suspected weak spots. Another feature of the Smart Cable Guard platform Helen wanted to test was the monitoring of 5 to 6 kilometres long feeders.
The Smart Cable Guard platform in operation at Helen Electricity Network
| Sensor 1 | Control Unit | Sensor 2 |
Benefits for Helen Electricity Network
Smart Cable Guard has been used as a proof-of-concept for online partial discharge monitoring of medium-voltage power cables and it fully met all expectations from Helen. One of the decisive features of Smart Cable Guard for Helen is that it is a proven and mature concept which is commercially available on the market. Helen continues to use Smart Cable Guard to explore the feature where the platform can detect faults and pinpoint weak spots within an accuracy of 1% of the monitored cable system. More in-depth information about Helen’s asset monitoring activities and the Smart Cable Guard project can be found on Helen Electricity’s website under Research and Development.