Maintence costs of Distribution System 2

[simatic7]

Hi All
We are preparing a maintenance schedule of Underground and overhead distribution system (11 kV) and we came across the cost of distribution system maintenace for budgetting purpose. Does anybody have an idea what is the tentative percentage of maintenace costs per transformer per km cable or how do you calculate the maintenance cost. If you have any idea pls let me know. Or even the maintenance costs in terms of total costs of the equipment and how does it distribute over the years.
Thnaks in advance

 

[Zogzog]

Sucha simple question with such a complex answer. Uptime magazine has many related articles to this subject.

Cables fail the most often, transformers fail the least often, but when a transformer fails it has the longest replacement time so it has about the highest failure "rate" in a power system, and they usually get the least attention from a maintenence aspect.

NFPA 70B and ANSI/NETA have recommended intervals for a relibility centered maintenence program, those intervals are based on the most economical factors for establishing a program.

The moment that the equipment in your substation is installed it will begin to deteriorate. This process is inevitable and if not checked will eventually lead to equipment failure and costly downtime. Additionally, changes that are made to the system, including loading, will result in improper equipment coordination and operation.

The function of an Electrical Preventive Maintenance (EPM) program is to recognize problems and to provide a means to correct them before failure occurs. Additionally, an EPM program will help ensure the safety of personnel operating or working near the equipment.

A good EPM program should consist of routine inspections, testing, repairs, and servicing of switchgear assemblies, transformers, circuit breakers, switches, relays, and support equipment.

A well organized program not only reduces costs of repairs, downtime, and hazards, it also help improve employee morale, increase productivity, and help find system deficiencies from installation or modifications.

Maintenance basics

Proper maintenance of electrical distribution equipment can be summarized by four simple rules:

1. Keep it tight
2. Keep it cool
3. Keep it clean
4. Keep it dry

These four rules will prevent many of the most common problems found in power distribution systems. The biggest contributors to equipment failure are:

? Overheating caused by high resistance connections
? Insulation deterioration from high temperatures
? Binding of mechanisms from dirt accumulation
? Tracking caused by surface contamination
? Reduced insulation properties from moisture absorption

Many facilities have some type of EPM program in place that falls under one of four basic philosophies.

Run to failure

This method can be summarized by the old saying, “If it Ain’t broke, why fix it?” Equipment is essentially allowed to degrade until a failure occurs, at which point the question “Why did it fail?” is asked. It never ceases to amaze experienced maintenance personnel why the same people that are opposed to performing preventive maintenance on multi-million dollars distribution system change the oil in their cars every 3,000 miles religiously.

Service as necessary

This method is simply done by observations and regular, informal inspections. Under this approach, obvious problems are addressed and corrected before failure occurs but no formal testing is conducted unless a problem is suspected. This method can be compared to taking your car into the shop when your service engine light comes on or a strange noise is heard while driving. Many industrial plants use this approach and find it to be a semi effective and economic choice.

Scheduled preventive maintenance

In this approach, established EPM is performed at fixed intervals of time, operations, or running time. These procedures are usually based on manufactures recommended maintenance intervals or industry standards. While this type of program ensures that equipment gets regular attention it does not take into account reliability, safety, or productivity significance.

Reliability Centered Maintenance

This approach utilizes such factors as reliability requirements, current equipment condition, and manufactures recommendations. RCM is the most reliable and cost effective approach to EPM because it improves plant reliability and reduces maintenance costs by focusing efforts on items that are most important or likely to fail. RCM is used extensively by the military and nuclear industries and is gaining acceptance in manufacturing plants where productivity and safety are a major concern.

 

[simatic7]

Thanks Zogzog for your complex answer to simple question and it was meant to be that and I wanted the way you did. I will find out the standard and check for that
regards
Simatic

 

[racobb]

Your background seems to be with computers and you are asking about distribution system maintenance costs? What is wrong with this picture?

Alan

 

[simatic7]

Thats true. My bachelor deg was electrical and masters in computer and after working in Unix for 7 years , again I started working as an electrical again so it is like that.

 

[Zogzog]

What I posted is just the start, one key piece of info is what it costs for you to be down. Power plants, data centers, high value manufacturing can all be thousands of dollars a minute for an outage, so they obviously would spend more on miantenence.

Here is the ANSI/NETA recommended intervals.