The Megger MIT1025 10-kV Insulation Resistance Tester is one of the best choices when it comes to insulating resistance measurement. With features to simplify and accurately assess…
Depending on the method of inspection, as well as application and installation, a great deal of time and effort could be invested in verifying the electrical health and integrity of electrical insulation. However, insulation resistance tests can be a relatively quick and effortless method of inspecting insulation. This type of test can be applied to practically any electrical insulation. Test results are recorded, trended, and if appropriate, compared to manufacturer’s recommendations or industry standards and guidelines. A good insulator should have a very high resistance to leakage current. Environmental, electrical and mechanical stresses can aid in exploiting voids and the development of microscopic cracks. These phenomenon permit increased access for contaminants to migrate into the insulator or insulating systems. When this happens, there is an increased potential for electrical faults and system failures, which relates to compromised reliability of the electrical system.
Insulation plays a very important role in an electrical system. Without electrical insulation, the electricity flowing in the conductors is exposed to short circuit to other conductors or create the risk of electrocution to personnel. It is important to always check the integrity of insulation to ensure the safety and reliability.
Circuit breakers are used everywhere – in our homes, offices, and electric facilities. The degradation of the electrical insulation that is an integral component of these protective devices, can be influenced from both environmental and operational stresses. Additionally, oxidation and ware of circuit breaker contacts can lead to relatively high resistance connections and overheating of the circuit breaker. In the worst case, contacts can become welded together, thereby defeating the protective intent of the circuit breaker. This is why it is important to utilize the proper electrical test equipment when testing, to ensure that the circuit breaker is properly fulfilling its intended purpose.
A Megger (insulation resistance tester) is a type of electrical test equipment used to verify the effectiveness of insulation to act as a barrier between energized conductors, or between energized conductors and ground. It is critical to the reliability of the electrical power system that there is a way to know when insulation has been damaged or compromised in any way.
An insulation resistance test is conducted to examine the effectiveness of insulation in a variety of electrical power system apparatus. Faulty electrical insulation is the source of dangerous shock hazards and can often cause ancillary damage to adjacent equipment as well. Routine electrical testing and maintenance can help to identify when insulation has deteriated before it reaches the point of failure, saving the expense of repairs and unplanned outages.
Testing electrical insulation can be quick and easy when using test equipment specifically designed to perform insulation resistance measurements. A good insulator should have a very high resistance to current flow. Factors such as temperature, electrical and mechanical stresses, weather and moisture ingress are all capable of adversely impacting the characteristic qualities of materials that make them such good insulators. The degradation of these materials over time can result in unplanned outages, safety concerns for personnel and an overall degradation of power system reliability.
The dielectric absorption ratio is the ratio of two time-resistance readings such as a 60-second reading divided by a 30-second reading. If the ratio is a 10-minute reading divided by a 1-minute reading, the value is called the polarization index. The principle behind the test is that the resistance would increase with time as the capacitive and polarizing currents begin to subside.
Unlike spot tests that are relative to specific conditions such as temperature each time that the test is performed, ratios of insulation resistance (Dielectric Absorption Ratio) that are taken at essentially the same time and temperature require no correction factor for comparison purposes.