Designing and installing an earthing system is one of the most important elements of solar PV system installation, because it guarantees the safety of the system and optimises its operation. An earthing system has the primary purpose of diverting possible fault currents that are generated by the system and sending them to ground, ie. to safety. Naturally, because solar PV systems are located externally and have the fundamental status of being exposed to weather conditions, they are vulnerable to the many electrical issues that are caused by fault currents and therefore earthing. So this could be gradual degradation of insulating materials in the solar PV system over time, or simply the effects of a lightning strike, for example. So grounding protects people and equipment by acting as an escape route for unwanted currents.
Therefore, an effective grounding system ensures that any exposed conductive parts of a solar PV system do not conduct dangerous voltage levels. This is done through the installation of various safety measures within the system, such as fuses, circuit breakers and safety switches. An earth continuity tester ensures that these safety measures are working as intended, when a fault occurs.
What is the purpose of an earth continuity test?
An earth continuity test checks the resistance between the earth point on the solar PV system and the Main East Terminal. A low resistance measurement means that when a current fault occurs, the current will flow to earth as intended, and it will not escape externally, meaning that anyone exposed to the live conductor could receive an electric shock, or the current could cause a short circuit, overheating or a fire. A high resistance means that this intended current flow is prevented, which would cause these problematic effects.
Because a solar PV system is exposed to the weather extremes, and for a prolonged period, its components are subject to physical damage, corrosion and general degradation. So the earth continuity test checks that the earth connection is undamaged by this possible system failure, and that the safety mechanisms within the solar PV system are still working to protect users of the system.
What instrument to use for an earth continuity test
The earth continuity test forms an essential part of the commissioning process for a solar PV system, but is also important as part of ongoing maintenance of the system. Because solar PV systems can degrade over time, in terms of the insulation resistance, it is essential that regular inspection and maintenance is carried out, and insulation resistance testing and earth continuity testing form a central part of that. The earth continuity test is also known as the earth bond test or the earth resistance test.
Through the earth continuity test, a testing instrument validates the compliance of the safety mechanisms. A common instrument used for earth continuity tests is a multi-function tester, such as the MFT-Pro supplied by Test Instrument Solutions. Multi-function testers help the professional electrician carry out a series of basic but essential electrical tests with one instrument, hence saving time and labour setting up and using different instruments.
In addition to the MFT-PRO, specific Solar PV testing equipment such as TIS PV-ISOTEST, TIS PVCHECKs & TIS PVCHECKS-PRO PLUS also have the capability to carry out continuity tests on exposed metal parts.