Power analysers are instruments used for measuring and analysing electrical power. They measure many electrical parameters, including current, voltage, power, harmonics, phase displacement and frequency. They are used to analyse the actual performance of an electrical system and to diagnose faults or problems. They are used by professional technicians in many areas, including the testing of electric motors, power transformers and the evaluation of high-voltage systems. They are also used in laboratories, power plants and for monitoring renewable energy sources.