Proactive Network Monitoring PQ 4p

7/21/2019 Proactive Network Monitoring PQ 4p

http://slidepdf.com/reader/full/proactive-network-monitoring-pq-4p 1/9

Marko Pikkarainen29.3.2012

Power quality and proactive network monitoring

Marko PikkarainenTampere University of Technology

The Department of Electrical Energy Engineering

[email protected]

SET-1520 New Applications in Electrical Energy Engineering27.3.2012


Content of the presentation

• 1. Power quality in general (EMC)

• Consequences of poor Power Quality

• Economical impacts

• Standard (EN 50160)

Power quality quantities

• 2. Some recent changes in the field of power quality

• Flicker

• 3. Proactive power quality monitoring

Power quality in general

• Power Quality: The characteristics of the electricity at a given point on

in electrical system, evaluated against a set of reference technical

parameters (IEC 61000-4-30)

• Electromagnetic compatibility (EMC): The ability of an electrical

equipment or system to function satisfactorily in its electromagneticenvironment without introducing intolerable electromagnetic

disturbances to anything in that environment

3


Consequences of poor PQ

•Poor power quality can have different effects. The range reaches from

disturbing effect on human beings (flicker) up to consequences on

operation of equipment.

•There are long term and momentary effects. Harmonics and unbalance

cause increased losses in the utilities equipment and reduce life time ofcomponents.

•Momentary effects are a sudden malfunction or damage of a device.

They commonly appear with the quality parameters such as: voltageinterruption, voltage dips and transient overvoltage.

•The most commonly reported symptoms of power quality phenomena

are light flickering, circuit breakers t ripping and computers locking up orrestarting. Also some damages are reported due to voltage quality

problems

4




Economical impacts of power quality

The importance of power quality problems can be reviewed by its

economic impacts.

•In the USA economical losses due to interruptions are estimated to be

between 104-164*109

dollar annually.•Other power quality problems are estimated to have 15-24*109 dollareconomic loss impact annually.

• Gross domestic product of USA was 14 526*109 dollar (2010)

5


Regulation and standardisation

There are several regulations, standards and laws that regulate the

distribution utilities actions and design and use of elect rical equipments

• national laws and regulations

• directives and standards

• general guidelines by field of business

EMC standard

• IEC 61000 series

6


61000- 1- x Gener al

61000-2-x Environment •Description of the environment•Classification of the environment

•Compatibility levels

61000-3-x Limits •Emission limits

•Immunity limits

61000-4-x Testing and measurement

techniques

•Measurement techniques

•Testing techniques

61000-5-x Installation and mitigation

guidelines

•Installation guidelines

•Mitigation methods and devices

61000-6-x Gener ic s tandards

61000-9-x Miscellaneous All the rest

EN 50160

• Standard EN 50160 defines, describes and specifies the main

characteristics of the voltage at a network user's supply terminals in

public low, medium and high voltage AC electricity distribution networks

under normal operating conditions. (EN50160)

Some problems :

• Covers only normal operation and even for that case only during 95% of time

obligatory

• For some power quality parameters only indicative values are given

• EN 50160 is not EMC standard, compliance with EN 50160 standard doesn‘tguarantee undisturbed operation of all devices

• Describes maximum values or variations of the voltage characteristics under

normal operating conditions which can be expected by the customer at any

place of the network

7


Voltage fluctuations and flicker

• Flicker (PST, PLT) is the subjective impression of luminance variations of lightning as a result of voltage

fluctuations.

• Flicker is more a physiological than a physical value.

• The flicker effect depends on: the amplitude of the relative voltage fluctuation and the repetition rate of the

appearance of the voltage fluctuation. With the same frequency of the voltage fluctuation the flicker effect isdirectly proportionally to the amplitude of the voltage variation.

• Flicker causes normally no damage of devices or an interference of their function.

• PST and PLT occurs without dimension (pu).

• The borderline was established laboratory tests with individuals. (for incandescent lamps)

8


t

u(t)

regular sinusoidal

voltagefluctuation

U

U

regular rectangular

voltagefluctuation

arbitraryrectangular

voltagefluctuation

U2

U

0.1

1

10

0.1

0.001

1

0.01

10

0.1

100

1

1000

10

10000 changes/min

100 Hz flickerfrequency

P =1st

[%]U

U




Very common reason for customer complaints (it is easy to observe)

Origins for flicker:

• starting currents of induction motors, fluctuating torque of load (stone crusher), weldingmachines, electro heat devices with thermostat, Electric arc furnaces

Remedial measures:

• Increase short circuit capacity of the network

• Starting current limitation

• Smoothing of load torque

• Avoidance of sharp load changes

• Automatic welding machines, 3-phase instead of 1-phase welding machine

• For EAFs: use of DC EAF, power-factor correction, use of dynamic compensation units

Limits in EN 50160

Under normal operating conditions, in any period of one week the long term flicker severity

caused by voltage fluctuation should be Plt 1 for 95 % of the time.

9



Under normal operating conditions excluding the periods with interruptions, supply

voltage variations should not exceed ± 10 % of the nominal voltage Un.

In cases of electricity supplies in networks not interconnected with transmission

systems or for special remote network users, voltage variations should not exceed+10 % / - 15 % of Un. Network users should be informed of the conditions.

Under normal operating conditions:

• during each period of one week 95 % of the 10 min mean r.m.s. values of the

supply voltage shall be within the range of Un ± 10 %; and

• all 10 min mean r.m.s. values of the supply voltage shall be within the range of

Un + 10 % / - 15 %.

10


Voltage unbalance

In EN 50160 voltage unbalance is defined as a ratio of the negat ive

sequence voltage and positive sequence voltage

Consequences of unbalance:

• Increase of the losses in the grid components• Increase losses and vibration moments in electrical machines

• Could increase non-characteristical harmonic currents of rectifier andinverter

Sources for unbalance:

• Non three phase loads (most of the loads in LV level / customer end)

• Railways

• Electric Arc Furnaces

11


1

2

U

U k

u

1

2

I

I I u

Voltage unbalance

Remedial measures

•Increase short circuit capacity of the network (network strengthening)

•Distributesingle phase loads evenly between phases, use three phase loads

•Disconnection via converter sets of a three-phase motor and a single-phase

alternator •Use inverters to change three phase system to single or two phase system

•Balancing using Steinmetz principle

Lim its in EN 50160

•during each period of one week, 95 % of the 10 min mean r.m.s. values of the

negative phase sequence component (fundamental) of the supply voltage shall be

within the range 0 % to 2 % of the positive phase sequence component

(fundamental). In some areas with partly single phase or two phase connected

network users' installations, unbalances up to about 3 % at three-phase supplyterminals occur.

12




Harmonics

When the waveform of voltage or current is not pure sine wave those can be

modelled using Fourier transform method (in real life it rarely is)

• Fundamental: Signal component that occurs with the line frequency

• Harmonics: Signal components which frequencies are multiple integer of the fundamental

• Interharmonics: Signal components which frequencies are not mult iple integer of the

fundamental (no limits in EN 50160)

• Subharmonics: Signal components which frequencies are below the mains frequency (nolimits in EN 50160)

• The classical harmonics-theory deals with frequencies from 0 Hz to about 2500 Hz (50 thharmonic, Bashir tell youmore about higher frequencies)

Consequences of harmonics:

• increase thermal and mechanical stress of the components and devices, increases grid

losses, might produce inf luence for r ipple-control devices, might produce f licker byinterharmonics.

13


Harmonics

Sources for harmonics:

• Power electronics

• Transformers, iron core inductor (in normal mode

effect negligible)

• Electric arc furnaces

Remedial measures:

• Power factor correction (passive, active)

• Central filter systems (also distributed)

• Changing of the mains circuits switching state, in

order to avoid resonances

• Increase short circuit capacity

Lim its in EN 50160

• during each period of one week, 95 % of the 10 min

mean r.m.s. values of each individual harmonic

voltage shall be less than or equal to the value given

in table

14


Odd harmonics Even harmonics

N ot mu l ti pl es o f 3 Mu lt ipl es o f 3

Orderh

Relative

amplitude uh

O rd e r h R e l at ive

amplitude uh

Order h Relat ive

amplitude uh

5 6,00 % 3 5,00 % 2 2,00 %

7 5,00 % 9 1,50 % 4 1,00 %

11 3,50 % 15 0,50 % 6..24 0,50 %

13 3,00 % 21 0,50 %

17 2,00 %

19 1,50 %

23 1,50 %

25 1,50 %

NOTE: Novalu esaregivenfor harmonicsof orderhigherthan25,astheya re

usuallysmall,but largelyunpredictabledueto resonanceeffects.

Frequency

The mains frequency is global quantity in interconnected networks. The

change in frequency is result of change between power production and

consumption. In interconnected networks with controlled reserves, the

frequency shows only low fluctuation.

• Frequency rise (more production than consumption)

• Frequency falls (more consumption than production)

Consequencesof abnormal frequency:

• clocks that run synchronously to the line frequency may face some problems

• Produce mechanical stresses in turbines

• Affects to uncontrolled synchronous- and asynchronous drives

15


Frequency

Remedial measures

• Use of reserve power plants

• Load shedding

Lim its in EN 50160

Interconnected 49,5 Hz - 50,5 Hz during 99,5% of a year

networks 47 Hz - 52 Hz dur ing 100 % of the t ime

Islanded 49 Hz - 51 Hz during 95% of a week

networks 42,5 Hz –57,5 Hz dur ing 100 % of the time

16




Voltage dips and swells short voltage

interuptions

Temporary reduction of the r.m.s. voltage at a point in the electrical

supply system when the voltage falls below 90 % of the reference

voltage

• voltage dip duration (from 10 ms up to including 1 min)

• voltage dip residual voltage (minimum voltage)

• swells are same as dips but voltage rises above 110 % of the reference

voltage

Consequences of voltage dips

• Problems with programmable logic controllers

• Problems with electronic devices (restarts of computers)

• Problems with asynchronous motors (halt, antiphase)

Produces costs: shut down costs, standstill costs, restart costs, additional costs

17


Voltage dips and swells

Sources for voltage dips• Faul ts

• Motor starting• Transformer switching

• Swells switching operations and

load disconnectionsRemedial measures• Use of dynamic voltage restorer

• Change of networks switching state

• Improve grid reliability

• Increase short circuit capacity of the network

Lim its in EN 50160• The vast majority of voltage dips has a duration less than 1 s and a

residual voltage above 40 %. However, voltage dips with a smallerresidual voltage and longer duration can occur infrequently. In some

areas, voltage dips with a residual voltage between 90 % and 85 % of

Uc can occur very frequently as a result of the switching of loads in

network users‘ installations

18


~ ~= =

~

as yr i sor switch

P

Q

grid load

rectifier

energystorage

inverter

Interruptions

Definition

• condition in which the voltage at the supply terminals is lower than 5 % of thereference voltage (EN 50160)

• prearranged, when network users are informed in advance; or

• accidental, caused by permanent or transient faults, mostly related to

external events, equipment failures or interference. An accidental

interruption is classified as:

• a long interruption (longer than 3 min);

• a short interruption (up to and including 3 min)

Consequences of interruptions

• Produces costs: shut down costs, standstill costs, restart costs, additional costs

Sources for interruptions

• Normally, interruptions are caused by the operation of switches or protective

devices. (faults)

• Maintenance of components

19


Interruptions

Remedial measures

• Decrease fault occurrence (overhead lines -> underground cables)

• Install remote controlled components to grid (switch, isolator)

• Build backup connection or backup power generation units for sensitive

customers

Limits in EN 50160

• Under normal operating conditions, the annual frequency of voltage

interruptions longer than three minutes varies substantially between areas. Thisis due to, among other things, differences in system layout (e.g. cable systems

versus overhead line systems), environmental and climatic conditions.

• The duration of most of the short interruptions may be less than some seconds.

Indicative values, intended to provide readers with information on the range ofmagnitude which can be expected, can be found in IEC/TR 61000-2-8

20




High frequency signals / Mains signalling

voltages

Signal superimposed on the supply voltage for the purpose of

transmission of information in the public supply network and to network

users' premises. Three types of signals in the public supply network canbe classified:

• ripple control signals: superimposed sinusoidal voltage signals in the frequency

range 110 Hz to 3 000 Hz;

• power-line-carrier signals: superimposed sinusoidal voltage signals in the

frequency range 3 kHz to 148,5 kHz (for PLC purposes, in some networks also

frequencies above 148,5 kHz are used.);

• mains marking signals: superimposed short time alterations (transients) at

selected points of the voltage waveform

Consequences of signalling voltages

• EMC problems might occur: the operation of touch dimmer lamps might be

disturbed by PLC (power line communication)

21


Transient over voltages

Short duration overvoltage usually with a durat ion of a few milliseconds

or less

Consequences of transient over voltages

• Breakage of devices and components

Sources for transient over voltages

• lightning, switching or operation of fuses

Remedial measures

• surge protective devices (For withstanding transient overvoltages in thevast majority of cases, LV Installations and end users’ appliances are

designed according to EN 60664-1.)

22


Some changes in field of power quality

23

Marko Pikkarainen 29.3.2012

Flicker sensitivity of compact florescent

lamps

• Flicker is the subjective impression of luminance variations of lightning

as a result of voltage fluctuations. Flicker is more a physiological than a

physical value. The tests to produce the borderline of flicker were

established in laboratory with individuals. This borderline is valid for

incandescent lamps.

• The result of the European Commission Regulation number 244/2009

is that incandescent bulbs will be gradually phased out from the market

• Compact fluorescent lamps have different flicker response because the

working principle is different

• Flickermeter is able to detect voltage changes with appearing

frequency from 0.05 Hz to 35 Hz.

24





lamps

25



lamps

26


Flicker measurement in future

• Same measurement method but new limit

• Valid for traditional voltage changes

• Interharmonics are not affecting to result

• New measurement method with modified lamp characteristic

and old limit (1 pu)• Interharmonics could be taken into consideration

• Replace flicker with rapid voltage changes

27


u(t)

variable gainT = 1 min demodulation

P

Pst

lt

weightingfilter lampe -eye

H(s)

squaring andsmoothing

statisticalevaluation

8.8 Hz 0.53 Hz0 .0 5H z 3 5 Hz

UU (t)

UU (t) weighted

% % %²

momentaryflickerlevell P

f

Proactive power quality monitoring

28




Traditional power quality monitoring

• Power quality measurements are based on centralized measurements

from MV level

• Outages, frequency problems and voltage levels in MV level have been

spotted from centralized measurements

• From LV side power quality is usually monitored with case specific

measurements

• customer complaints and clarification requests

• There has not been available comprehensive and continuous power

quality information over entire distr ibution network

• The novel AMR technology and distribution substation automation hasincreased the power quality awareness

• Of some power quality quantities:

• Interruptions, voltage levels, harmonics...

29


Power quality monitoring in the future

•Power quality monitoring will need information from voltage from each

customer connection point

• AMI is obvious system to produce the needed data

•In addition of voltage measurement a proper current measurement could

provide critical information to power quality monitoring application

•AMI could short the clarification t ime of power quality disturbances and

make it more efficient

•If the clarification time decreases also it could speed up decisions and acts of

how to decrease the effect of disturbance

•Savings

•Also customer satisfaction level could increase

30


Proactive power quality monitoring

Goal:

• To detect power quality and reliability problems automatically

• To detect the most probable reason for power quality problems

automatically

• To predict the behaviour of different power quality quantities in thefuture

• Short term prediction (operations)

• Long term prediction (planning)

• To improve power quality, to operate network optimally

Methods:

• efficient utilization of static and dynamic information

• optimization of network monitoring processes and information

management

31


New model of proactive network monitoring32


Network

Information

Customer

Information

Measurements(AMR, conditionmonitoring,

PQ, weather,relay data, etc.)

Future

scenarios

Standards,

recommendations

•Analysis

•Detection ofpotentialproblems

•Priorisation

Immediate

actions

Proactive

actions

Operation

Maintenance

Planning



Example of proactive network monitoring,

Flicker

33


Network

Information

Customer

Information

Future

scenariosMeasurements(AMR, condition

monitoring,

PQ, weather,relay data, etc.)

Standards,

recommendations

•Analysis•Simulation•Detection ofpotential

problems•Priorisation

Planning

REFERENCES

H. Renner, M. Sakulin, Power quality, T extbook to lectur e “Power quality and supply reliabil ity“

H. Renner, “Power quality and supply reliability“ , Lecture notes

M. Pikkarainen, B. A. Siddiqui, P. Pakonen, P. Verho, S. Vehviläinen, 2011, “ Vision of Power Quality Monitoring andManagement in Future Distri bution Network s”, Conference paper, CIRED 2011.

M. Pikkarainen, P. Nevalainen, P. Pakonen, P. Verho, 2010, "Practical Case Study: Measurement of Power QualityProblems Caused by Common New Loads “, Conferenc e paper, NORDAC

“T he Cost of Power Disturbances to Industrial & Digital Economy Companies” , 2001, Consortium f or ElectricInfrastructure to Support a Digital Society.

European Commission Regulation, 2009, implementing Directiv e 2005/32/EC of the European Parliament and of the Council

with regard to ecodesign requirements for non-dir ectional household lamps, No 244/2009.

RongCai, 2009, “Flicker Interaction Studies and Flickermeter Improvement”, Dissertation, Eindhoven University of

Technology, Netherland

EN 50160, 2007, “Voltage characteristics of electricit y supplied by public distributio n networks” , Standard

L. P. Frater, N. R. Watson, “Lig ht Flicker Sensitiv ity of High Efficienc y Compact Fluorescent Lamps”, Power EngineeringConference, 2007. AUPEC 2007. Australasian Univ ersities

34


Thank you for your attention

35


Documents

Proactive Network Monitoring PQ 4p