Electrical Maintenance Types And Examples

Electrical Maintenance Types And Examples
Electrical maintenance

I work as electrical maintenance engineer. Our team is responsible for maintenance of almost all electrical equipment types. Low voltage equipment and medium voltage equipment. such as but not limited to:

  • Low and medium voltage electric motors.
  • Electric transformers, 25KVA up to 2.5MVA
  • Overhead transmission line, 11KV network
  • generators.
  • Lighting poles and systems.
  • Medium voltage VSD panels.
  • EX and hazardous areas electrical panels and motors.

The number one priority is to catch the faults before it happens. TO do this we apply preventive maintenance program for all electrical equipment. Let’s discuss what is electrical preventive maintenance?

What is Electrical maintenance?

Electrical maintenance is the process of electrical systems inspection, testing, monitoring and replacing all electrical parts as required, using hand tools, thermal imaging, computerized programs and special measurement devices, to keep systems and machines working efficiently and safely.

Electrical maintenance usually performed by an electrical engineers and electricians with good experience and knowledge.

What are electrical maintenance tools?

I use many electrical maintenance tools during my work. Some maintenance tools we use are listed below:

  • Hand tools, such as, cables cutter, insulated pliers, insulated screw driver, hacksaw, spanners and wire stripper and hammers.
  • Measurement devices, such as, AVO meter, insulation resistance tester (megger tester) and grounding resistance measurement devices.
  • Testing devices, such as, transformer oil break down voltage tester, CB and overload tester and transformer turns ratio tester.
  • Other maintenance tools and equipment like, transformer oil filtration unit, Thermal imaging camera and vacuum cleaners for panels cleaning.
  • Maintenance computerized programs such as MAXIMO and ORACLE maintenance.

All these maintenance tools and equipment may involve in our electrical maintenance activities. Each task has its own requirements of tools and devices. You should prepare your tools and devices first, then start your maintenance task.

Maintenance types and strategies

In general, maintenance strategies and types are:

  • Corrective maintenance.
  • Preventive maintenance.
  • Predictive maintenance.

Corrective maintenance

Corrective maintenance It is task performed to identify, isolate, and repair a fault which is actually happened

This electrical maintenance approach is based on that the costs for equipment repair in fault cases are lower than the cost required for a complete program of maintenance

Preventive maintenance

Preventive maintenance, also referred to as PM, is a planned maintenance that means performing regular time based maintenance on electrical equipment, So that it wouldn’t break unexpectedly. The maintenance program is similar to your car periodic maintenance.

The main purpose of preventive maintenance is to reduce the equipment unexpected failing chances and to control the machine condition.

Preventive maintenance is driven by time, meter or event-based triggers. It’s mainly based on the assumption that a machine will degrade within a given period of time that is common for its all type and is determined by the equipment manufacturer. The relevant parts will be , replaced, removed or rebuilt on before the expected failure point.

Preventive Maintenance Disadvantage

  • Preventive maintenance requires a little more cost. Of course keeping the equipment ready needs spare parts i.e more cost.
  • You’ll need enough labor on hand to make this periodic work. Again, more money!
  • More work potential because of over activity of maintenance. This means you will need to well train the labors to do the work safely.

Its clear that you pay money to get the advantages of the preventive maintenance. Keeping you assets in a good condition and your system in a high efficiency can pay you the extra money you need for implementing this maintenance program.

Suppose you have a generator renting organization. You have the choice to save some money of doing preventive maintenance for generators, or to pay some money for spare parts, extra well trained labors and implementing the maintenance program.

If you choose to save some money. You will for sure pay more than you save when customers argue the faults and unexpected shutdown of your generators.

The wise is to pay some extra money and in exchange get more customers who will pay you more money. With some of this more money you pay the labors and the spare parts for your generators.

Predictive maintenance

Predictive maintenance is determined by the condition of equipment rather than expected life statistics. Predictive maintenance evaluates the condition of equipment by performing periodic (offline) or continuous (online) equipment condition monitoring.

By monitoring the machine during normal operations predictive maintenance tries to predict failure before it actually happens. A scheduled repair is planned at a time that minimizes the impact on production when predictive analysis spots an issue.

Predictive maintenance technologies

To evaluate equipment condition, predictive maintenance utilizes nondestructive testing technologies such as infrared, thermal imaging, partial discharge, corona detection, rotating machines (like electrical motors) vibration analysis, sound level measurements and electrical transformer oil analysis

Preventive vs Predictive Maintenance

Preventive vs predictive maintenance is important for every maintenance person. Both preventive maintenance and predictive maintenance are designed to reduce failure and to increase asset life span.

The difference between preventive and predictive maintenance is

  • preventive maintenance is scheduled regularly, while predictive maintenance is scheduled based on asset condition.
  • Preventive maintenance is easy and costs less to implement, While predictive maintenance may require additional workers and training of existing personnel.

preventive vs predictive maintenance Example:

Preventive maintenance example:

  • In our live the preventive maintenance is around us, as an example when you make maintenance for your car periodically based on time, you are doing PM for your car
  • In electrical work life, If you have a three phase motor, you can make a check list of parts to be replaced, cleaned or maintained monthly or after a specific period of time regardless the condition of this part.
  • In my work we faced a continuous repeated motor bearing failure. The motor bearing get completely damaged. In some cases we find the rotor damaged to. The solution we decided to do was a good preventive maintenance program. The Pm program depends on working hours of the motor. Each working year we stop the motor and replace the motor bearing, regardless its condition.

Predictive maintenance example:

The same organization has a running preventive maintenance program, but there are risk of over greasing the bearings, so ultrasound analysis device is good for scheduling the greasing work orders. 

In this case besides the cost of the ultrasound analysis  device, an additional training for workers to use this device is required.

Main difference between Preventive  and predictive maintenance

  • Preventive maintenance is scheduled at regular intervals, while predictive maintenance is scheduled based on asset conditions  (as needed).
  • Predictive maintenance is performed only when needed, it reduces labor and material. However, implementing a predictive maintenance program requires money for training, and resources.
  • Both maintenance programs need a good computerized maintenance software for scheduling, like MAXIMO Computer Maintenance Management System,  and ORACLE Maintenance Management System

Routine maintenance for electrical equipment

Electrical periodic maintenance should be done for electrical motors, generators, lighting systems, control circuits and switchgear.

A preventive maintenance check list may include cleaning, oil changes, lubrication, repairs, inspecting adjustments, and replacing parts of the equipment, this is regularly scheduled based on time and equipment. Let’s have a look at preventive maintenance for some electrical assets.

Preventive maintenance for electrical generator

Electrical generators have two parts, mechanical and electrical. The mechanical part is the engine. I made maintenance for electrical part only. The mechanical team take care of the engine. So, let’s discuss the preventive maintenance of the generator electrical parts.

Weekly bases generator maintenance:

  • Measure generator output voltage and current using a multi-meter and compare it to the readings of the generator meter.
  • Check battery charger output current and voltage.
  • Check battery voltage.
  • Check the generator control circuit for any loosen connections or terminal corrosion. Finding any corrosion early prevent faults and shutdown.
  • If the generator is outdoors, check its parts sealing. Make sure no dust enters the control panel.
  • If the generator is stand by, start it and keep it running for 15 minutes to charge batteries.
  • Make sure the generator is connected to a good earthing network.
  • Keep the batteries clean.

Yearly bases generator maintenance:

  • Check stator resistance by megger tester.
  • Check rotor resistance.
  • Check vibration and make sure the generator bearing is not damaged.
  • Make sure the fan has a secure guard.
  • Make sure the generator emergency shut down is working properly.
  • Check output voltage, current and frequency and record the data.
  • Inspect exciter and armature windings. Make sure no corrosion in the wires.

Electric Motor Preventive Maintenance Tips

For electrical motors some of maintenance are periodically done to keep the motor running in a good condition. Some activities are done while motor is running and others are done with motor stopped.

  • Check motor temperature rise using thermal imaging.
  • Check Motor voltage and current.
  • Check motor vibration using a vibration measuring tool.
  • Check motor earthing cable connection.
  • Measure earthing resistance and make sure its value is < 5Ohm
  • Check motor lubrication. Make sure to follow the motor nameplate lubrication period.
  • Make sure to record all data and findings.

For more information about, how to check electric motor, check out the detailed article here.

Control circuits routine maintenance

Electrical control circuits and panels don’t have the same components, as each circuit has its own requirements

But in general you should keep the panel or the circuit in good condition by performing some basic periodic maintenance, some are listed below

  • keep the panel clean and dust free.
  • check panel working voltage.
  • check the panel for any abnormal noise.
  • thermal imaging for the panel components.
  • measure current if necessary.

I have written a detailed article about electrical maintenance work, you can find it here.

Lighting systems periodic maintenance

  • turn on lights and check any damaged lamps
  • check photocell if found
  • clean and keep the panel clean
  • check control contactors for any abnormal noise
  • check voltage of the lighting panel
  • thermal image the components for any temperature rise

Electric Transformer Preventive Maintenance Tips

Oil immersed transformers are electrical stationary machines with oil tank and some other accessories, below are some periodic maintenance for them.

  • Check transformer temperature rise using thermal imaging. And compare it to the transformer temperature gauge.
  • Check transformer voltage and current. IF the transformer is a medium or high voltage transformer, you an get the voltage and current readings from the switchgear.
  • Check transformer noise, make sure its as normal. This check step needs an expert labor to do it.
  • Check transformer earthing cable connection.
  • Measure earthing resistance and make sure its value is < 5Ohm
  • Check transformer oil leakage on it body or under its base. If there is any oil spillage, check its source. Make this daily.
  • Check silica gel color. Make sure its not saturated by moisture. Make this daily.
  • Check oil level in the conservator tank. If the transformer is hermetically sealed, then check oil level gauge.
  • Check cooling fans and oil pumps. Make sure it work properly in hot days and stop in cold ones. In many cases we find the cooling fans closed by plastic bags. Which lower its cooling capacity.
  • Yearly task is to clean bushing.
  • Make sure to record all data and findings.

Read also my other detailed article about transformer most common 7 faults. Also, check out my article, electrical maintenance work. It has more detailed transformer maintenance.

Why is Preventive Maintenance Important?

Implementing preventive maintenance for electrical assets is important and can help both the organization and the workers. We all know how can preventive maintenance help the organization! But how come it helps workers?

Let’s have an example of real workplace of mine. Me as an electrical maintenance engineer, work for a leading company in the oil and gas field. Before we implement a good preventive maintenance program for overhead power lines, we faced several unexpected faults and shutdown situation.

Here is one of the greatest faults we faced, some poles are wooden poles. Unexpectedly we got many calls in several times that one or more wooden pole caught fire. In this case, Both the fire fighting and electrical maintenance team should react quickly to stop the fire and reconnect the power to the oil wells.

These fire incidents happened day and night. What do you think will happen if we find a solution for this problem?  Yes, That’s right! All fire fighting as well as electrical team members will be satisfying.

That happened already when we find that the root cause of the situation was the earthing cable of the insulators need to be fixed. We did it! Earthing for all wooden poles. Imagine how we all are very satisfying! Of course the organization took its part of satisfaction too.

Now let’s answer the question:

Why is electrical maintenance importance?

Performing regular electrical maintenance for assets increases the overall efficiency for all equipment and has the following importance:

  • Assures equipment working in optimal condition and increases the reliability of the assets.
  • Longer equipment life time.
  • Reduces major repairs numbers and corrective maintenance activities.
  • Saving unexpected faults down time and money. Planned maintenance makes the team ready with all needed spare parts, this shorten the down time.
  • Increase efficiency of the whole system.
  • Increase safety at workplace. Doing regular planned maintenance is much safer than repairing unexpected faults, which can happen any time, day or night.
  • Save money on production loss due to unexpected shutdown.

 A planned PM is better compared to actual breakdown downtime of the equipment. You control your time and the team performance is better than working under unexpected faults repairs.

Find out more details about maintenance importance in my article here.

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