Summary:A shunt is a resistor that has low, known resistance, and is placed in parallel with the current-car...
A shunt is a resistor that has low, known resistance, and is placed in parallel with the current-carrying conductor. Energy shunts are used in a wide variety of applications, including current measurement and power circuits. They offer an accurate alternative to Hall effect sensors and current transformers.
Shunts can be used to increase the accuracy of current sensors, reduce circuit voltages or reduce costs in energy metering systems. They are available in a range of sizes and shapes to handle different amounts of current. Some are designed to be placed in the return leg of a circuit, which eliminates the high common mode voltage to ground that can damage components or cause unwanted emissions.
In the case of a prepayment meter, shunts are used to reduce the amount of electricity or gas that is consumed by the customer.
This is important because it allows the meter to run at lower capacity, and thus prevents people from overusing energy and running out of credit. The shunt also helps to protect the sensor from overheating, which can cause failure of the unit.
There are a number of different ways that customers can top up their energy, either using a smartcard, token or key, or by taking cash into a PayPoint, Payzone or Post Office branch. Some older prepayment meters can be topped up by inserting coins into the device, but these are now largely phased out. People can also use online or mobile apps to add credit to their accounts.
As energy bills have risen and real incomes have fallen, pressure has been mounting on suppliers to stop forcing people who cannot afford their prices onto prepayment meters. Last year Citizens Advice estimated that 3.2 million households ran out of credit on their prepayment meters, with many being temporarily disconnected from energy as a result.
Although you can still be moved to a prepayment meter if you fall behind on your energy bill, it is against the law for suppliers to do so in certain circumstances, as set out by Ofgem. This includes if you are disabled or have a condition that makes it difficult for you to get near the meter, or if your home is a long distance from shops where you can top up your meter.
Suppliers can only fit a new prepayment meter if they have made at least 10 attempts to contact you and carried out a site welfare visit, which is usually done by someone who will wear body cameras or audio equipment to record the process. You can also ask to be moved away from a prepayment meter if you are worried about being cut off, or if your situation changes and you no longer need to buy your energy that way.
If you’re concerned that your supplier is breaking the rules, you can contact Ofgem to report them. You can also get help from a free and independent advice organisation.