A PQ Case Study

Case study 42 Total Power Quality Management

A PQ Case Study

APQI (C) Copyright 2014 (December 2014) All Rights Reserved 1

A PQ Case Study

CS 42 ENG 14

Total Power Quality Management

In

An Automotive Component Manufacturing Unit


A PQ Case Study


42 Abstract: Power quality is a measure of ideal power

supply system. The disturbances or

deviations from desired power

parameters i.e. voltage, current and

frequency can be either through grid, a

neighbouring user or self generated

issues. At times, a plant could face power

quality issues generated within its plant

boundary and outside it. In order to

improve productivity and quality,

manufacturing facilities are adopting

automation in most of the industrial

processes. All these automation processes

are equipped with sensitive electronic

components. These electronic equipments

are susceptible to any deviation in power

quality like voltage surge/sags, voltage

and frequency variation, transients,

electrical noise, harmonics etc. Any of

these power quality related issue can

cause damage to sensitive equipment

resulting in loss of capital cost of the

product, reliability of operation, loss of

productivity and economic loss.

The case study depicts case of an

automotive component manufacturing

facility facing power quality issues due to

internal and external factors. The case

study also highlights various mitigation

techniques adopted by the plant team to

successfully mitigate such issues.


A PQ Case Study


Introduction Delphi-TVS is a joint venture between Delphi Corporation, USA and T.V. Sundaram Iyengar

& Sons, India manufacturing Diesel Fuel Injection Equipment for Cars, Sports Utility and

Multi Utility Vehicles, Light Commercial Vehicles, Tractors, Single & Two Cylinder engines.

Delphi is the largest automotive supplier in the world and TVS is the largest automotive

systems supplier in India. Delphi-TVS Diesel System was started in 1990 as a joint Venture

between Lucas, UK and LucasTVS, Chennai Subsequently on Delphi acquiring Lucus

Factories, Delphi TVS became a joint venture between Delphi, US & Lucas.TVS, Chennai

The Factory is located at the Thiruvallur, Sriperumbudur Road and is 6 km from

Sriperumbudur in Tamil Nadu State of India. It receives power through an 11 kV feeder and

step down to 433 volts using a 750kVA transformer.

Fuel injection system of a vehicle is very complex and needs precision control for better

combustion and efficiency of the system. In order to achieve this, manufacturing process of

fuel injection system is very sophisticated. The accuracy of product required is around 1

micron. To achieve this accuracy, the plant invested in capital intensive and state of the art

equipments .

Demand of the vehicles is related to economy and season. The demand of the product is

directly related to vehicle market and highly fluctuating. In order to meet this fluctuating

demand and not to miss any market opportunity Quality Power on 24/7 basis is imperative.

Background: The plant was set up in the year 1990 and considering the uncertainty of the business,

every possible care was taken to minimize the investment. The investment was also

minimized in power distribution system. To start with a demand of 500kVA plant team

decided to install one number of 750 kVA transformer with off load tap changer. The plant

acquired two numbers of 310kVA, 415 Volt overhauled DG set from parent company, Lucas

TVS.

At the time of installation, plant received its supply from an 11 kV feeder which was running

near to the plant. This feeder was also catering power requirement of various loads like mix

of industries, domestic and agricultural. Length of line was around 20 KM and most of its


A PQ Case Study


length, it was running through agricultural fields. Distance of substation was around 12 kM

from the plant.

Figure – 1 shows single line diagram of the supply line and various loads on it.

Fig – 1 Supply to TVS Delphi

Figure 2 below shows distribution of power in the plant. As shown in figure 1, the plant receives power from state utility.

Fig – 2 Distribution system of plant

Domestic

Load

Agricultural Domestic

Load Load

Supply from

substation


A PQ Case Study


The plant started getting various problems due to power quality issues. The problems were

related to external factors as well as internal issues.

Problem Faced by plant:

Power quality issues faced by the plant are broadly identified and classified into two

categories viz. external issues and internal issues.

External issues

1. Frequent Interruptions :

The plant used to get too many interruptions both due to various technical reasons

and natural causes. Some of the reasons for interruptions were due to falling of the

trees on the line, particularly in the monsoon. During harvesting season, frequency

of breakdown faults used to increase due to additional power drawn by agricultural

load which was more than the capacity of the transmission line. Another reason for

interruption was due to falling of electrical pole carrying the distribution line due to

heavy winds.

Apart from frequent interruptions, location of fault and addressing it used to take

number of days as most of its length, distribution line used to pass through fields and

inaccessible for fault location.

2. Unbalance Voltage :

The feeder supplying to TVS-Delphi also supplied power to domestic and agriculture

sector. Plant is located around 12 kM from the substation. Preceding and succeeding

plant, the feeder is connected with domestic and agricultural loads. Most of the

loads at agriculture and domestic sector were single phase loads. Due to use of

single phase loads on the feeder, voltage un-balance was unavoidable.

3. Voltage variation:

The plant also faced problem in voltage level of the grid. Voltage variations were

from 8 kV during Day and 12kV during midnight was common. OLTC at the SEB

substation was not functional and transformer opted by the plant team was without

OLTC.

4. Sequence Change after Power restoration :


A PQ Case Study


After resumption of Power caused due to breakdown, lines were interchanged by

mistake (after Replacing new poles/ rerouting of lines) resulting in phase sequence

change.

5. Fuse Blowing Structure:

As the Horn-Gap fuse (HG Fuse) used was visually available for examination,

frequent fuse blowing was noticed. In addition to the above as per the practice of

SEB, lighting Arrestor was placed before fuse and failure of lightning arrestor led to

surges and transients. This used to cause HG Fuse blowing. As a result of this, there

used to be complete absence of one or more Phases.

Internal issues

Apart from above mentioned problems faced outside the plant boundary, there were

problem present within the plant which were later attributed to poor power quality. The

problems faced by the plant were:

1. Frequent Tripping of Sensitive Equipments

2. Failure of Power Supply in the CNC Equipments

3. Burning of neutral at R&D

4. Software corruption of CNC programs

Impact on Business

All above issues were resulting in loss of productivity and service quality. Issues arising due

to poor power quality were affecting the business. Various effects due to poor power

quality were:

1. Customer dispatch was seriously affected.

2. Purchase of costly tools resulting in increased M/C tools.

3. Too Many Electronics Failures resulting in increased down time.

4. Increase in Scrap & Rejection cost

All above parameters have a direct impact on profitability of the business. In a way, poor

power quality was having an impact on profitability of the business.


A PQ Case Study


Analysis: In order to find root cause of the problems faced by the plant, power quality audit was first

carried out in the year 1993-94. Power quality study was carried out to identify presence of

disturbances in power parameter viz voltage, current and frequency. Measurements were

carried out to identify problems caused in various equipments.

Due to frequent unscheduled interruptions caused from the grid side, plant was forced to

use DG set quite frequently. There were various problems faced by the plant when

operating on DG set. Detailed measurements were carried out on when plant was operating

on DG set.

Voltage:

Figure – 3 shows voltage profile at the DG set during starting of heavy load. As seen in the

graph, voltage dips were recorded on R-phase when heavy loads were started. Voltage dips

were as low as 196 Volts.

Fig – 3 Voltage profile at DG

Frequency:

Figure 4 shows impact on output frequency through DG set during switching of loads. As

seen in the figure, when motors up to 35 kW were switched on, there were dips in


A PQ Case Study


frequency. When motor of 90kW was started, frequency dips were severe to trip some CNC

machines.

Fig – 4 Frequency profile at DG

Dips in frequency and voltage were causing tripping of machines, thus affecting productivity

of the facility.

Neutral to ground voltage:

Figure – 5 shows neutral to ground voltage at the DG. Ideally, neutral to ground voltage at

the DG should be zero. But as seen in the figure, there were impulses in neutral to ground

voltage. At some time, these impulses were of the magnitude of 105 Volts and could be

damaging to electronic equipment.

Fig – 5 Neutral to Ground voltage


A PQ Case Study


Figure – 6 voltage waveform output of the DG set. As seen in the figure, voltage waveform is not sinusoidal.

Fig – 6 Voltage waveform

Measurements of harmonics were carried out at the output of DG set. Figure – 7 shows

voltage harmonics at the output of DG set.

Fig – 7 Voltage harmonics

As seen in the figure 7, total voltage harmonic distortions were 11.2% which is quite high.

Among particular order of harmonics, 3rd, 5th and 7th were predominant harmonics.

Presence of voltage harmonics could cause various problems like malfunctioning of relays or

circuit breakers, burning of neutral conductor due to triple-n harmonics and failure of

electronic component.


A PQ Case Study


During the power quality study it was also identified that there was electrical noise present

at various CNC machines. Due to presence of noise, malfunctioning of machines and

resetting of machines were observed.

Mitigation Techniques – Phase 1: Based on power quality audit and problems identified by the plant team, various mitigation

techniques were adopted. These mitigation techniques were also divided under two

categories viz source and load.

Mitigation techniques on load:

Presence of noise was affecting performance of CNC machines. It was recommended to

install isolation transformer at the equipment Level to mitigate the Noise produced by

various equipments. In order to mitigate noise, Isolation Transformers were installed and

Neutral to Ground Voltage was measured daily and was found to be less than 2V.

Due to switching of load, voltage dips were observed when plant was operating on DG sets.

As a Temporary measure, plant changed operating practice to avoid voltage dips due to

switching of loads. Motors above 50 HP were started first and then power was resumed to

the equipments whenever power was supplied through DG set.

As plant was in expansion mode, plant team discussed noise problem with CNC machine

suppliers so that mitigation techniques can be build in the machine itself. Machine

manufacturers incorporated power quality mitigating techniques in the machines. They

supplied new CNC machines with noise cut off transformer, filters for drives and even

redesigned machines to suit the available power quality.

Mitigation adopted for supply:

Power quality from the grid was a major concern for reliable operation of the plant. But due

to various issues from state electricity board, and subsequent DISCOM the grid could not be

up graded. As a temporary solution, the plant team decided to install voltage stabilizers to

ensure regulated voltage supply to critical loads through DG sets. TVS Delphi invested

around INR 25 lakhs (2.5 Million) on voltage stabilizers. As there was no improvement of the

grid condition, TVS Delphi had no option but to invest on captive power plant. Existing Two


A PQ Case Study


numbers of 310 kVA DG sets were replaced with 2 nos. of 1000 kVA DG Sets. TVS Delphi

invested around INR 65 lakhs per DG set. Total investment incurred for installation of DG set

was 130 lakhs. In addition management approved for hiring 1 no 1000 kVA DG Set as a

Temporary measure till the SEB Supply was improved. Two DG Sets were operated for

feeding critical Loads operating 2 Shifts/day. Monthly cost of operating DG set was around

INR 40 lakhs per month.

Benefits:

By installing captive power plant and taking all possible mitigating measures, TVS Delphi got

following advantages:

Meeting Customer Schedule – Timely delivery of the consignment due to improved

reliability in operation

Space saving – When plant was operated before installation of new DG sets, voltage

stabilizers were used to ensure regulated voltage supply to critical loads through DG sets.

After installation of new DG sets, critical loads were always supplied through new DG sets.

This measure made voltage stabilizers redundant and were removed. Removal of voltage

stabilizers resulted in substantial space saving.

Saving additional working day: Due to non reliability of operation, lot of time used to be

lost due to breakdowns. Along with the improvement in reliability of operation, decrease in

breakdown time was also realized. This resulted in meeting targets in 6 working days in a

week instead of earlier case of operation which was 7 days a week. Reducing operation from

seven days a week to six days a week resulted in cost saving in terms of reduced energy

consumption and lower manpower cost arising due to overtime. Total additional cost that

used to be incurred due to operating 7 days a week was around 10 lakhs a day. Annual

additional cost was around INR 520 lakhs a year. By saving additional working day, around

INR 500 lakhs per year were saved.

Mitigation Techniques – Phase 2

After taking corrective measures in the first phase, TVS Delphi was left with few problems.

The problems faced by the plant were:


A PQ Case Study


Increased Power Cost: One of the major problem faced by TVS Delphi was operating cost of

DG sets. Due to increased cost of diesel, power cost was increasing and plant team were

under pressure to reduce Cost. Energy cost from DG set was around INR 22 per kWh where

as using captive power plant it was INR 11 per kWh. Electrical energy cost from state

electricity board was INR 7 per kWh. Initially total electrical consumption of the plant was

around 1,200,000 kWh per month. Out of these, 70% of electrical energy was generated

through DG set. In current scenario, energy consumption has increased to 2,500,000 kWh

per month. Around 30% of this energy demand is met through captive power plant.

Table – 1 shows electrical energy demand and source of generation.

Before Now

Total Consumption 1200000 2500000 kWh

DG 840000 0 kWh

Captive 0 750000 kWh

EB 360000 1750000 kWh

Table - 1

Tripping of load: Apart from operating cost of DG set, there were also complaints regarding

tripping of load during change over.

Mitigation technique: Plant team identified a 1.9MW Power Plant with furnace oil as fuel to

replace 3 no's of 1000 kVA DG Set. By commissioning this 1.9 MW captive power plant with

an investment of 4.5 crore. TVS Delphi addressed all the above issues and power cost was

marginally costlier than SEB Power. However, chiller motors used to create voltage dips due

to their frequent starts and stops. To reduce operating cost further and avoid voltage

related issues arising out of chiller compressor motors, present chillers were replaced with

Vapour Absorption Heat Pump utilizing the waste heat from flue gas of captive power plant

exhaust. This resulted in further reduction in power cost which was now close to that of SEB

besides eliminating voltage disturbances due to starting/Stopping of Chiller Motors.

However, with ever increasing cost of oil, cost of generating electricity from captive power

plant was increasing with every rise in fuel price. Plant team started following up state

electricity board vigorously to supply additional but Quality Power to meet the increasing

Demand. After 3 years of constant follow up, SEB authorities agreed to extend Supply at 33

kV but in phased manner.


A PQ Case Study


Table – 2 shows annual loss suffered by the client due to altenate source of electrical energy

instead of SEB.

Before Now

Total Consumption 1200000 2500000 kWh

DG 840000 0 kWh


EB 360000 1750000 kWh

Cost of power generation through

DG 22 22 INR/kWh

Captive 12 12 INR/kWh

EB 7 7 INR/kWh

With SEB as base, annual loss: 151,200,000.00

45,000,000.00

INR per year

Table - 2

In order to reduce operating cost from captive power plant, TVS Delphi team took the task

to ensure 100% usage of SEB power when available. However as mentioned earlier, SEB

power has its own issues that does not support reliable operation of the plant. In order to

avoid any voltage variation from grid side an 11kV/11 kV AVR (continuous correction) in

addition to Step variation at 33 kV Side by OLTC. A 6.3 MVA, 11 kV /11 kV AVR was installed

to correct input voltage variation range 9 kV to 12 kV. This addressed issues of voltage

variation. Investment made for AVR was around 50 lakhs.

However an AVR will not protect operation against abrupt or unplanned power failures. In

order to protect plant against un-scheduled power cuts, UPS were installed for critical loads

of following capacity. TVS Delphi invested 143 lakhs for UPS system of following rating.

500 kVA x 3 No’s

550 kVA x 1No’s

160 kVA x 4 No’s

Apart from above measures, the plant ensured that it is protected against other power

quality problems by taking following measures.

Use of Sandwich Bus bar trunking using Copper Cadmium in place of conventional

Aluminium Bus bar trunking

Maximum Capacitor used to be restricted to 25 kVAR (To reduce Transients)


A PQ Case Study


Where Load is Fluctuating use of Thyristorised APFC in place of conventional APFC

Use of MCCB in place of conventional Fuse Switches (To ensure simultaneous closing

of all phases)

Use of 4 core conductors (for strengthening of Neutral Conductors)in areas like Data

Centres which use Single Phase UPS (To mitigate the effect of Third Harmonics )

Use of Filters (Chokes) at the input and output to mitigate the effects of 5th &7th

Harmonics.

Use of Circuit Breaker /Load Break Switch in place of conventional Air Break Switch

plus Horn Gap Fuse Combination at the receiving point of SEB Supply.

Summary:

TVS Delphi is a classic example of an industry which faced almost all kind of power quality

issues. They faced problems in continuous availability, quality (voltage and frequency

related issues) and cost (higher cost for DG or captive power plant).

They started solving problem of continuous availability of quality power and installed DG

sets. However, some of their problems were solved but new problems were raised. They

started paying high cost of power which was adding to their expenses and hitting bottom

line. But determined and committed plant team addressed all power quality problems. One

of the major reasons to take power quality so seriously was its impact on business. Poor

power quality was affecting business in a negative way and in order to improve business it

was imperative for the plant team to improve power quality which they did. In the process

of this, they also reduced operating cost of the plant.

Table - 3 below summarises various issues faced by the plant and mitigation action taken by

the plant team.

Sr. No Power Quality issue Solution adopted

1. Non reliability of power DG sets

2 Noise Isolation Transformer

Filter


A PQ Case Study


Re-design of equipment to suit power quality

3 Voltage quality Improved operating practice

Higher capacity of DG sets

4 Cost of electricity Adopting low cost fuel

Improving efficiency of system

Better utilization of available grid power by

installing AVR

5 Reliability of operation Installed UPS system

Higher size of neutral conductor

Lower size of capacitors for APFC

Table - 3

Even after taking so many mitigation measures, plant is suffering a loss of around INR 60-65

lakhs per month due to power quality issues. Table - 4 shows various capital expenditure

incurred by TVS Delphi to overcome various power quality issues. Total capital expenditure

made by TVS Delphi to address various power quality issue was around INR 325.5 Million.

Capex cost INR

Cost of 1000 kVA DG set 130,000,000.00

Voltage stabilizers 2,500,000.00

UPS system 143,000,000.00

AVR 5,000,000.00

Captive power plant 45,000,000.00

Total 325,500,000.00

Table - 4

In case if there were no mitigation measures adopted by plant team, there would have been

high cost in terms of energy cost that plant had to pay annually. Table-5 below shows

avoided cost due to various mitigation measures.


A PQ Case Study


Parameter Before Now

In case if mitigation measures were not adopted

Total Consumption 1200000 2500000 2500000 kWh

DG 840000 0 1750000 kWh


EB 360000 1750000 750000 kWh

Cost of power generation through

DG 22 22 22 INR/kWh

Captive 12 12 12 INR/kWh

EB 7 7 7 INR/kWh

With SEB as base, annual loss:

151,200,000.00 45,000,000.00

315,000,000.00 INR per year

Table - 5

Table – 6 shows various losses associated due to poor power quality issues.

Operational cost INR per year

Power quality cost due to various power quality issues - Is saving or still incurring losses?

78,000,000.00

Additional cost due to electricity generation with DG set and captive power plant

48,000,000.00

Cost reduction due to shifting from 7 days a week to 6 days a week. This cost include all costs including manpower, energy, inventory etc.

52,000,000.00

Avoided cost due to improved reliability of supply from EB 315,000,000.00

Table - 6

From the case study it can be seen that poor power quality can cause increased operational

cost. Increased operational cost directly impact profitability of the business. It is very

important to maintain power quality as desired.


A PQ Case Study


About the author:

Mr. P. Premkumar

Mr. P. Premkumar holds Bachelor’s in electrical and electronics

engineering, Masters in energy management, PG diploma in

maintenance management, certified energy manager and lead

auditor in ISO 14001-2004, 18001-2007 ISO 50001-2011.

Mr. Premkumar has 36 years experience in maintenance of electrical

and electronic systems including power management and compliance of Statutory

Regulation. Out of 36 years, he has 29 years of experience in selection and installation of

industrial electrical system. He has 15 years of experience in areas related to energy

management. During his career he has accomplished various achievements like establishing

maintenance management systems starting from Scratch in 2 factories, playing key role in

establishing TPM and QS /EMS relating to maintenance. He has carried out several

Improvements to reduce power cost and down time.

Apart from this Mr. Premkumar has successfully established infra structure for power and

utilities to facilitate expansion activities. He has also worked in the area of optimization of

manpower for maintenance, skills improvements of maintenance team, preparation of

electrical safety manual to enhance awareness on electrical safety.

Mr. Premkumar was also team leader for the team which won award on National Energy

Conservation conducted by CII during 2007, 2009 and 2010. He has also participated in

several knowledge sharing forums organized by CII,PCRA,BEE etc., Mr. Premkumar is

currently working as DGM (Works Engineering) at Delphi TVS Diesel Systems Ltd.

Disclaimer: The sole responsibility for the content of this document lies with the authors. It does not represent the opinion of

the Asia Power Quality Initiative and ICA network. APQI and ICA network are not responsible for any use that may be made

of the information contained therein.

A PQ Case Study

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