Searching for mistakes, errors, faults and potential dangers is called inspection. It’s not the process of maintenance, repairing or correcting these faults and errors.
When do You Need electrical inspection?
I do electrical inspection in my work for:
- New equipment we purchase for the work to make sure it’s as we require.
- New electrical projects and installations before energizing them.
- Periodically for old installations and equipment to find out any faults, errors or hazards.
- Overhead power lines quarterly to find out any insulation cracks or cutout fuses hot spots to repair or replace it.
- For third party companies before working in our company’s oil fields to make sure they are safe to use.
In this article, I will share with you all my experience about how to perform effective electrical inspection for transformers, motors, distribution panels, lighting systems and more!
Why are electrical inspections important?
Electrical inspections are important for the safety of resources and lives because, its principle is to search for errors and faults before they become a potential hazards.
Well, these are the fundamental needs while sometimes you need just more than these two. Such as.
Avoid damage
Some devices are not just replaceable in a second. Some devices can be imported or sensitive.
It will be a big problem if they go out of order even for a few seconds. Some devices take too much time to start working. In industrial areas, the orders have to be completed in a very small time period. Such kind of scenario could cost millions to the owners.
To avoid such kind of scenario, it is advised to get your electrical systems inspected before starting a new order.
Otherwise, the damage that is done to the electrical systems often leads to some disastrous conclusions.
Monetary benefits
The defective device often leads to more energy consumption and lesser efficiency. It even leads to heating up of the electrical outlets and may cause a fire eruption. But, to avoid all of this we have to get our electrical systems inspected periodically.
Defective wires may lead to cause defects in the electrical devices. Defective wires could cause surges and short circuits that effects the health of electrical equipment.
So, to save yourself the grand cost of bills or the equipment that you may lose due to negligence.
Not violating the law
Every country imposes some rules and regulations on their nationals to follow. Such as a very common rule is household and industrial meters.
Household users cannot use an industrial meter and vice versa. There are rules that state whether to use certain devices at home or not.
If you get the electrical system of your home, the engineers may suggest such kind of advice to use a device or not.
So, conclusively we can say that electrical inspection is important because it detects any faulty work done by an immature, reveals problems (such as grounding done near your building), identify old and outdated wiring, spot erratic appliances, and check for electrical hazards for the safety of live, money and infrastructure
Electrical inspection for transformers
Electrical transformers are some kind of machines! of course they are static machines with no movement, to keep these machines in a good condition you should make electrical inspection regularly.
This electrical inspection guide will provide you with the most common check points for electrical transformers.
Inspection before energizing the transformer
Before the transformer is energized, visual inspections should be done as follows:
- check nameplate of the transformer, and compare the data with the project requirement (i.e. primary and secondary voltage, frequency, KVA rating etc.)
- check oil level in the conservator tank, make sure its 1/3 volume is full.
- check for any oil leakage on transformer body. Read my article about Transformer Oil for more information.
- check that radiator has no plastic bags or birds nests between its sections.
- check for any mechanical damage due to transportation, specially the radiators because its a weak point..
- check all bolts are well tightened.
- check cooling fans and oil pumps connection. Read my article about Transformer Cooling Methods. for more information about cooling methods of the transformer.
- check protection of the transformer (like buchholz and sudden pressure relay).
- make sure that high and low voltage bushings are in a good condition, have no cracks and are clean.
- Check silica gel color, ensure it’s not saturated.
After energizing the transformer
After the transformer is connected, and before it is energized make sure that primary and secondary windings are connected to the right side.
Double check the voltage of the high and low voltage sides.
After loading the transformer keep inspecting its temperature rise and make sure its not exceeding the allowable one on the nameplate.
The temperature is shown on the temperature gauge, but its better to use temperature detector to ensure that the gauge is working properly.
While the transformer is in service, the same electrical inspections mentioned above should be done periodically to keep the transformer condition under your eyes.
Every year the oil of the transformer should be tested and analyzed to make sure it still clean and moisture free.
Induction motor electrical inspection
The main parts of induction motors are stator and rotor. In some larger size motors some instruments are added such as space heaters, thermo-couples, cooling fans and junction box.
Each of these parts and accessories need maintenance program, this what I will discuss below.
electric Motor inspection before installation
Before connecting the electric motor and energizing it, you ,as an electrical engineer or electrician, should visual check the motor for any damages, and chek name plate data as following points:
- voltage and frequency must be suitable to the source.
- nameplate current should be double verified to check the motor control panel components, set over-current protection and to check the size of the cable feeding the motor.
- motor rotational speed (RPM) should be suitable for the mechanical load.
- frame of the motor should be suitable for installation condition and place.
- explosion proof protection of the motor if needed.
- IP rating of the motor should be suitable to the application. I’ve a detailed article about IP rating, you can read it from for more information.
- motor connection, star or delta connection.
After connecting and energizing the motor
- check and measure grounding of the motor body, its resistance is accepted below 5 Ω.
- check voltage between motor phases and compare it to name plate value.
- measure motor current in both cases, no-load and loaded compare with rated value.
- check rotation direction.
- listen carefully to the motor for any abnormal noise.
- after loading the motor for at least two hours, check its temperature.
Motor periodic inspection
The motor is in service, works well and causes no issues! that’s good, but it doesn’t mean that no preventive maintenance needed for the motor.
While the electrical motor is in service a good preventive maintenance should be performed carefully, keep measuring and recording voltage, current, grounding and temperature values every one month, and keep comparing with nameplate values.
I have a detailed article about How to Megger A Motor? Read it from here for more information.
Electrical Lighting inspection
Lighting fixtures and lamps are used in all work locations and fields. In your house lamps are controlled by a switch.
While in large industrial locations lighting fixtures are controlled by panels contains relays, MCB‘s, photocell, contactors and many components.
Periodic inspection for lighting fixture
Lighting fixtures electrical inspection is cost-less, All you need is to be turn lights at night, you should have a clear vision of how many lamps are not working.
One effective method we rely on at my work is the report from the area supervisor. The company I’m working for is very large, we have lighting fixtures every where.
Each area, say oil plant or gas plant, the supervisor, who is not an electrician, report any damaged lamps to us, maintenance team to replace or repair.
Lighting control panels inspection
Like any electrical panel, keeping the panel not sealed allows dirt and dust to enter the panel and make connection issues for contactors, MCB’s and connection terminals.
In some cases dust, humidity or rain cause serious short circuit inside the panel.
Make sure the panel IP is suitable for the workplace environment, ensure it’s closed and sealed. I’ve a detailed article about IP Rating, you can find it here for more information.
Check Tips for lighting panels
- check panel door and openings, all should be sealed.
- check contactors for abnormal noise.
- clean the panel if it has any dust, But isolate power first.
- check voltage and record its value.
- test the operation of the photocell by covering it with a black piece of paper, lighting should work.
- check wiring for loosen connections, dust and corrosion terminals.
- make sure the panel is grounded, measure the grounding resistance and record it.
How do you inspect a DC motor?
DC motor inspection is very important. Some tips when you are about to inspect your dc motor are:
Surge Comparison Test
Insulation weaknesses and short circuits in the windings are tested using the surge comparison test. The capacitor inside the motor is charged and then this charge is conducted on one of the phases of the motor. The other two phases are grounded.
The motor will attain a voltage. If the test voltage, which is based upon the value of inductance of the motor, is attained without frequency deviation.
Then we can say that the turn-to-turn insulation test has been passed by putting a system through a surge test.
Polarization index test
The test of detection of the moisture and cleanliness of the motor is called the polarization index test. Two values are recorded. The first value is recorded after 60 seconds and the second value is recorded after 10 minutes have passed.
Then a ratio is taken in which a 10minute value is divided by the 1minute value. Then this ratio is compared with the data in IEEE 43-2000 standard. The comparison tells us whether the moisture level and cleanliness level are permissible or not.
DC High Potential (Hi-pot) test
A high potential is applied to the dc motor. Almost a 75k voltage is applied to test that the motor should not burn even at that much high potential.
When and how should you inspect power and hand tools?
There are some tools and their inspection methods mentioned below:
Clamps:
- Remember clamps are for temporary jobs not for the permanent lifting of the hoist objects.
- Swivels should turn freely.
- Moving part must be clean and lubricated.
- Frames and spindles should not be bent.
Pliers:
- Pliers must not be used to hammer or cut a wire.
- Pivot points and joints must be firm.
Wrenches:
- All sizes of wrenches must be available.
- The jaws should not be worn-out.
- The grips should not be worn-out or absent.
- Wrenches should not be deformed.
Mallets and hammers:
- The heads should not be damaged.
- Grips if present should not be in aworn-out state.
- Handle and the hammer must not be loose.
- There must not be any cracks in the handles or the heads.
Screwdrivers:
- Screwdrivers must be electrically insulated.
- Insulation should not be broken or worn-out.
- Shanks should be straight and sharp enough to hold.
- The tips of the blades should be straight.
Power hand tools:
Check power hand tools prior any use to make sure they are safe for work. Specially if you are about to use a power tool you usually not use or you share with others. Also, check power tools if you are about to store it for a long period without usage.
Power hand tools check tips:
- Should be properly insulated.
- Should not be showing any signs that they were used where they were not meant to be used.
- Check if the batteries or the power supply of the tool is working fine.
- Check the cord if it has one. Make sure it has no cuts cracks, frying or damages.
- Check the power plug and make sure it has no loose, faulty prongs or cuts at its connection point with the cord.
- If the power tool is wet never use it until making a deep inspection.
- Check the body and hands for any cracks.
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