A Comprehensive Look at Electrical Maintenance: From Preventive to Corrective Maintenance

I work as electrical maintenance engineer. Our team is responsible for maintenance of almost all electrical equipment types. Low voltage 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 prevent the faults before it happens. To do this, we apply a 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 do we need for electrical maintenance?

thermal imaging for a transformer
Me, doing thermal imaging for a transformer

Or, we can ask it as, 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, cable 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 one way or another.

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.

I have written a detailed article about, All Maintenance Types (6 Types), you can find it here. Check it out for more detailed information.

Corrective maintenance

Corrective maintenance, is any task performed to identify, isolate or repair a fault which is actually happened.

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

We call it “Run To Fail” because, we just let the equipment run without any type of repair until it falls and stops running, in this case we repair or replace it.

You may think about corrective maintenance as a bad maintenance strategy! well, its not bad all the time.

Some electrical equipment and devices require no maintenance during its life span! Think about the light bulb, isn’t it a clear example for corrective maintenance equipment? Yup, it runs to fall!

One more example is fuses, no maintenance as well. All you do, put the fuse into service and let it to fall.

Let’s think about another example. What about small motors in an industrial building? The motor cost may not too much compared to the cost of doing periodic maintenance for it. Its much better to let it runs to fall.

Preventive maintenance

Preventive maintenance, also referred to as PM, is a planned maintenance and performing regular time based maintenance on electrical equipment, so that it wouldn’t break unexpectedly. 

This maintenance program is similar to your car periodic maintenance, it’s based on Kilometers the car run not on the car condition.

The main purpose of preventive maintenance is to reduce the equipment unexpected fault  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 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 repeated motor bearing failure. In some cases the rotor got damaged too. The solution we decided to do was, a good preventive maintenance program. The PM program depends on motors working hours. Each working year we stop the motor and replace its bearing, regardless its condition.

Why is Preventive Maintenance Important?

Implementing preventive maintenance for electrical assets is important and can help both the organization and the workers as well.

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?  Yup, That’s right! All fire fighting as well as electrical team members will be satisfied.

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 important?

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.

Preventive Maintenance Disadvantage

  • Preventive maintenance requires a little more cost. Of course, keeping the equipment ready needs in stock 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 your assets in a good condition and your system in a high efficiency can pay you back the extra money you need for implementing this maintenance program.

For instance, If you have a generator renting organization.

You have the choice either 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 you make your customers happy and 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 example:

The same organization, the generator org. mentioned above,  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.

Predictive maintenance technologies

To evaluate equipment condition, predictive maintenance utilizes nondestructive testing technologies such as:

  • Infrared temperature measurement device
  • Thermal imaging camera
  • Partial discharge
  • Corona detection
  • Vibration analysis device
  • Sound level measurements
  • Electrical transformer oil analysis, and break down tester

Preventive vs Predictive Maintenance

Both preventive maintenance and predictive maintenance are designed to reduce failure and increase asset life span.

The difference between preventive and predictive maintenance is

  • preventive maintenance is scheduled regularly
  • 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  and predictive maintenance Main difference

  • 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

For detailed information about maintenance for electrical equipment like, motor, generator and transformer read my article here.

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