Monitoring Power Losses at Scottish Power Energy Networks Substations

Power grids provide the fastest and most cost-effective way to deliver energy from generation facilities to the point of consumption. However, transmission and distribution networks involve losses like any physical system, and the amount of energy injected to the grid will always exceed the amount of energy delivered to utility customers.

Power grid losses can be both technical and non-technical. The power dissipated in the form of heat by transmission lines, transformers and other grid equipment is a technical loss, while energy not billed due to incorrect metering or theft is a non-technical loss. It is important to note that technical losses have an environmental impact because they represent energy generation that never serves a useful purpose, while non-technical losses only have a financial impact because the energy is used but not accounted for.

Network losses have negative consequences for both utility customers and their clients. For the utility company, losses represent energy that must be purchased or generated but which is not billed to customers, driving up operating expenses without a corresponding increase in profits. For energy consumers, network losses are reflected as increased electricity rates; the utility company must include losses in their energy pricing to remain profitable and operational.

Energy-Saving Opportunities in Electrical Substations

Substations are a very important element of power grid infrastructure. They contain transformers that step down transmission voltages to a level that is better suited for distribution, and also contain key protection and control equipment. However, many energy losses occur at substations:

• Substation equipment dissipates large amounts of energy as heat, especially large transformers. All that energy must be generated by power plants to compensate.

• In addition, the substation itself requires energy to operate. For example, transformers are typically cooled with oil, which must be pumped. Substations also use application-specific equipment such as air compressors, dehumidifiers and battery chargers.

• Since the substation building must be kept under optimal conditions for occupants, there are also lighting and space heating expenses.

• The substation itself also needs a step-down transformer for operation. Since large power transformers step down voltage from transmission to distribution levels, it is necessary to have a separate smaller unit to step down voltage for appliances.

Scottish Power Energy Networks (SPEN) are a utility company serving parts of Central and Northern Scotland, and they wanted to identify energy-savings opportunities in their substations. Through a partnership with Edinburgh Napier University and Logic Energy, SPEN are monitoring losses and unmetered energy at multiple  substations in Glasgow area, selected to be representative of their grid as a whole.

Breaking Down Energy Expenses at Substations

A utility company can measure the energy consumption of its substation to get an idea of the operating cost, but this information by itself does not allow targeted actions to improve energy efficiency. To make improvements possible, first it is important to know how the energy consumption of a substation is distributed among the existing equipment – in other words, SPEN require an energy consumption baseline. Some electrical and mechanical systems in substations are mission-critical and cannot be shut down, but lighting fixtures and space heating equipment can be controlled according to occupancy with the goal of minimising their running cost. Scottish Power Energy Networks and Edinburgh Napier Universitycontacted Logic Energy to take the lead for this part of the project.

Although the project has the goal of analysing how much energy flows into each of the substations being monitored, it is equally important to determine how this energy flows internally once delivered to the substation. This is accomplished by installing a monitoring system at the main distribution board, capable of measuring the energy delivered to each branch circuit together with an study of the fabric of the substations too. The advantage of this approach is that the knowledge gained can be applied to other substations of similar design and layout. If energy savings opportunities are identified, deployed and validated for a few substations representative of the grid as a whole, results can be replicated elsewhere.

SPEN selected some of its  substations for in-depth energy monitoring, considering them to be representative of their overall network. The main substations selected are located around the Glasgow area.. Once the energy consumption of these  substations is broken down by system, each proposed measure can be analysed with precision, in terms of both energy consumption and environmental impact. In a subsequent step, monitoring and control of these systems  is planned for additional substations, although with lower data resolution.

Other than monitoring energy consumption directly, the scope of the work includes measuring indoor and outdoor temperatures, along with lighting levels. The purpose of these measurements is to optimise HVAC and lighting output and operation and further improve energy efficiency.

Substation Monitoring Goals

After monitoring has been deployed to break down the energy consumption of substations, targeted measures can be proposed. The following are some promising examples, but only monitoring allows a precise assessment of their effectiveness:

• Lighting upgrades and smart controls: In general, an LED fixture with lighting controls saves more than 80% of the energy compared with an equivalent HID fixture without controls.

• Equipment controls: Cooling and pumping equipment associated with substation heat dissipation can be optimised as well. Motor-driven equipment that operates intermittently can be equipped with a variable-frequency drive to reduce energy consumption significantly.

• Building envelope improvements: Heating and cooling expenses can be minimised if unwanted heat flows are controlled.

In general, measures that are proven effective in SPEN’s substations considered for the project can be replicated throughout the entire grid infrastructure to achieve large-scale energy savings and increased efficiency. Logic Energy plays a key role, establishing the consumption baseline against which energy-saving measures are assessed, and also measuring performance after measures are implemented by Napier University, allowing SPEN to assess their financial viability. The Scottish Energy Center will be performing energy modelling and infrared thermal imaging to validate the effectiveness of these measures and future actions to control them

Logic Energy monitoring and control systems offer the flexibility and scalability required for this project, with a track record of more than a decade across many business sectors – including the energy and utility sector industry. Logic Energy monitoring systems are plug-and-play and customisable, delivering real time data for a single location or across thousands of measurement points. The information gathered is aggregated and processed to deliver metrics that are useful for business decisions via the cloud.