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Why Insulation Resistance in Marine Electrical Systems Is Important

When it comes to running a proper audit of your electrical system, insulation resistance is one of the critical indicators to the health of the yacht electrical system. As the name suggests, the insulation resistance is the ability of the insulation material to resist the electrical current flow. From the time that you install your insulation, it begins to age and erode, and this deterioration impacts the performance of the insulation. Running regular audits to maintain the quality of your electrical insulation will reduce the risk of fire, overheating, shortages, shock, and more.

Insulation resistance tests are also known as Megger tests, which uses a high resistance meter with a test voltage of about 500 volts dc. The test is performed by applying a current limited DC test voltage between the conductors and the chassis of the equipment (ground).  The test voltage, or test current, is typically placed for the industry standard of one minute, which ensures all readings are based on the same length of time. During this time, the interval should either remain steady or drop steadily depending on the size of the system.

Any current leakage is to be measured across the insulation’s dielectric materials. The current may be measured in Milli-amps or Micro-amps and then calculated into Meg-ohms of resistance. The lower the current value, the greater the insulation resistance. As IR testing can be sensitive to temperature, readings should also be taken in both warm and colder temperatures so that comparison points are normalized for temperature.

When reading an insulation resistance test, it’s important to understand that what is normal should be considered relative to the yacht. So instead of comparing your readings to the readings of another boat, you should compare the regular readings of your boat over time for the most value. It’s also important that you are consistent in the tests that you perform and how they are performed to ensure that the data being compared is as similar as possible.

There are many types of insulation resistance testing that can be done on a yacht all depending on the size and complexity of the yacht electrical system. For example, when new machinery or electrical equipment is installed, it is important to run a “Proof Test” to ensure that not only the new equipment is in the condition needed to work properly, but also provides a baseline measurement for the equipment to be compared to in the future. In addition to Proof Tests, there are also spot reading tests which bases it’s results on a current being applied for a single 60 second interval, time resistance tests which include multiple successive readings at fixed intervals, and step voltage tests which involves testing insulation at two or more voltages and comparing the results.

By performing insulation resistance testing you are more easily able to identify things like current leakage. Much like leakage in a water pipe, an imperfection in wiring insulation can allow for electricity to leak, which can cause damage to electrical circuits and machinery over time. Routine IR testing can help identify these leaks more quickly, which helps improve overall boat safety and the health of your yacht electrical system. To schedule one of our professional yacht electricians to perform a comprehensive insulation resistance test on your yacht or boat or any of our other extensive marine engineering services please reach out to our experienced sales staff.

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