Automation of distribution substations improves visibility of the low voltage (LV) network and helps a utility company to utilise the power network in an optimum way. The first step of distribution automation is monitoring distribution transformers and, due to the importance of this asset, monitoring of critical parameters is essential.
Transformer monitoring can bring a lot of benefits for utility companies, including the capacity to:
- Recognise when transformers are on the brink of collapse (overloaded) and take remedial performance related actions. Often a utility may lose a transformer because of a lack of information around how the transformer is running.
- Improve visibility of the low voltage power network and help utility companies to deliver high quality electricity to customers. This system provides real time information about voltage, power factor, current, harmonics and unbalance from the LV network; and based on this information, utility companies can utilise specific remedies to solve problems as they occur.
- Decrease outage duration. If one transformer collapses, it is normally replaced within a period of 12-24 hours. However, automation can recognize transformer or outgoing LV feeder outages or problems and send an outage signal to the central system. With information that is provided by this system the utility company can recognize an overloaded transformer and can prevent it from collapsing.
- Utilise the useful information from the transformer monitoring system and make decisions about distribution network planning such as critical points in the network that need to be extended or upgraded. For example, this system is able to identify if transformers are working with more than 75-80% of their capacity, providing the utility company with a clear view of which parts of the power network need extension.
- Access useful transformer monitoring information for asset management and preventive maintenance.
- Utilise precisely measured delivered energy; and if all customers fed by this transformer are equipped with smart meters, the system can calculate LV network losses. LV network loss is a very good indication of weak points in the network and part of a strategy to improve overall losses.
- Send a central system command to intelligent electronic devices (IED) in the distribution substation, such as the streetlight feeder.
Inhemeter, through long-term cooperation with different utilities around the world, has established a distribution transformer monitoring system (as part of Inhemeter’s smart grid solution) to help utility companies improve automation of distribution substations and make the LV power network more visible (see figure on page 17).
Inhemeter’s distribution transformer monitoring system is composed of the IHM-3000-D intelligent device, which is responsible for measuring and gathering critical parameters from the transformer, acting as a CT connection meter to measure energy flow of the transformer. The intelligent device also acts as a data concentrator to communicate with and gather data, events and alarms, from subsidiary smart meters and send all the information to the central system.
IEDs (like the smart contactor for controlling the streetlight feeder or feeder management device that is responsible for monitoring and management of outgoing transformer feeders) can receive command signals from the intelligent device, and with flexible inputs and outputs the intelligent device can receive signals from other IEDs and send related command signals to IEDs.
A split current transformer aids the installation of the intelligent device to facilitate measurement of the secondary transformer and central system that is responsible for generating the information from the intelligent device, processing and analysing information, generating the related report and transferring related command and configuration to IEDs and intelligent devices. MI