T&D World have recently published an article about Pacific Gas & Electric Co (PG&E) – a gas and power company for California – and their efforts to reduce SF6 usage in all high-voltage gas-insulated equipment. PG&E have been increasingly committed to reducing their SF6 footprint since 1999: in fact, by 2002 they had already reduced their SF6 emissions by half.
But here is what is particularly interesting about their recent efforts: they want to phase out SF6 completely and they have 15 years of data on why it leads to will reduce operational costs and remove the risk of further regulation.
There is more leakage than you think. And it costs more money than you think
SF6 equipment suppliers claim that their leakage is under the accepted 0,1% limit. The study done by PG&E based on the data they have been collecting for 15 years shows that the real leakage rate is much higher. In fact, the average leakage in California totals around 2%, which is 20 times higher than the official data. Such discrepancy results not only in massive environmental impact, but also it significantly increases the operating costs. More leaks simply mean more money spent on additional SF6 gas purchases. Additionally, it is estimated that fixing a single SF6 leak costs on average $25,000.
Evaluating SF6 alternatives
PG&E have conducted a market analysis of available alternatives of SF6 and, after suppliers were invited to take part in the request for information, the company ended up with 3 solutions for high voltage gas insulated switchgear (GIS) and dead tank circuit breaker (DTCB): Novec 5110 insulating gas, Novec 4710 insulating gas, Dry air/vacuum. These three technologies were evaluated based on the following criteria: technical, regulatory and commercial. A single alternative to SF6 was preferred as this lowers the gas management risks.
Dry air/vacuum is the most cost-effective alternative to SF6
As a result of evaluation, the most cost-effective and environmentally friendly solution chosen to adopt was dry air/vacuum. This was concluded based on the following reasons:
dry air/vacuum does not contribute to global warming and has the lowest-cost life-cycle option;
it meets the upcoming California Air Resources Board (CARB) regulations - its leakage does not need to be reported which reduces costs significantly;
it is the most extensively available product in the industry and is available from multiple suppliers.
Preparing for the future without SF6
By the end of 2024, SF6 will be banned from all the equipment of 72kV or less in California; by 2030 – for all high voltage ranges. This regulatory phase out by California Air Resources Board could set a strong precedent for other regions. For example, the European Commission tried already to ban SF6 (in the framework of its F-Gas Regulation No. 517/2014) in 2014, but it did not affect the electrical industry. The regulation will be reviewed in the upcoming years.