Close encounters with analyses in the distribution system

Doc. Eduard Kaluš, Ing. Igor Chrap iak, Ing. Tomáš Burdan

Why do we need such analyses?

Because not enough details are known about what actually happens in a distribution network, modern phenomena, character (non-linear) of loads, asymmetry are underestimated

Because experts do not like to accept and nor do they address the existence of various new phenomena that exist in networks

Because we still live in the captivity of knowledge of ages old values and proven conditions, which no longer actually exist

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Objectives of analyses – detailed information

Data for customersData for administrators and operators of a distribution networkData for suppliers and dealersData for dispatching and producersData for the parent systemData for other partners in the energy market

Documents for:Analysis of network statusOptimization of connectionIncreasing efficiency and reducing lossesSolving undesirable and fault conditions Support of integration and management of renewable energy sources Support for electromobility...

What else do we deal with?

RMS voltage and current value, active power, reactive power,Apparent arithmetic power, apparent true power, distortion power (single-phase and three-phase), asymmetric power (AC), qualitative parameters of electricityCos , P/F, coefficient of increase in losses

Immediate values, RMS values, average values

Losses: minimum potential, increased due to reactive, distortion power and asymmetric power

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What is new in Slovakia?

Act No. 251 on Energy § 95Decree No. 358/2013 ME SR, which lays down the

procedure and conditions in the implementation and operation of intelligent metering systems in energy (IMS)

4 categories of end users supply points3 categories of functionalities of the intelligent metering system

Basic functionality Advanced functionalitySpecial functionality

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Summary report in accordance with the EN50160 standard

We began with TS, we continue through the resources to the end users

The report evaluates deviations from the EN50160 standard for frequency, voltage fluctuations, flicker, power asymmetry and THD U for each substation separately

Possibility of setting a monitored period and group of substations

Division into critical and non-critical variables of substations – the limit for critical values of substations is adjustable

Automatic and manual mode

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Summary report in accordance with the EN50160 standard

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Summary report in accordance with the EN50160 standard

Course of flicker L1, L2, L3 in the monitored period

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Summary report in accordance with the EN50160 standard

Course of voltage L1, L2, L3 in monitored period

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Table performance report

The report evaluates the P/Sr power factor with the ratio of reactive Q, distortion D and asymmetric power N with respect to the apparent power Sr

The possibility to set the monitored period, critical limit of P/Sr, minimum value of Sr and group of substations on which the report will be conducted

Based on results, we can determine which substation has high losses and which component of performance is the cause

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Table report on power ratio

Analysis of the report

More than 11% of the monitored substations have an average (weekly) power factor P/Sr less than 90%What does that mean? What would correction provide us with?

After increasing the power factor to 90%, we will reduce losses by 5.5 MWh (per week) – totals 3.7% of the active power After increasing the power factor to 95%, we will reduce losses by 7 MWh (per week) – totals 4.5% if the active power

What else will it bring us?Temperature rise of transformers and conductors –increased durabilityReduced load on zero conductorsMore efficient use of generation and transmission capacityIncreased use of the efficiency of electricity

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Table report of substation performance

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High reactive power drastically reduces the power factor

S (red), P+ (green), Q4 (orange)

Table report of substation performance

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Current asymmetry causing losses

Report on substation performance

The report evaluates the load of individual substations according to their maximum allowable current – the result is shown as real-time outside the tolerance and as percentage of time

Adjustable limits for alarms (lower and upper), for critical time limit, monitored period and groups of substations

Automatic and manual mode15

Report on substation performance

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Report on substation current

An alternative to the previous report on the evaluation of maximum current, which was conducted on individual substations with regard to the maximum allowable current

Possibility to set upper current limit, critical time limit, monitored period and groups of substations on which the report will be conducted

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Report on substation current

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Reality

Minimal losses exist under which it is not possible to get Real losses exist that are kz times higher than minimum lossTransmission of electricity is loaded (above) losses “due to”:- higher harmonics in i - phase shift of 1st harmonics between u and i- asymmetric consumption in 3f grid- unbalanced consumption in 3f grid

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Power factor cos & P/S, losses

cos – measurement according to custom in power, includes the effect of Q PFa = P/Sa (“cos” Sa) – measurement using so-called arithmetic apparent power, includes the effect of Q, DPFr = P/Sr (“cos” Sr) – measurement using so-called apparent true power, includes the effect of Q, D and asymmetry of N

cos( )

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2

2min

2 1PFP

SIRIR

kz 2

2

2

2

2

21 1

PN

PD

PQkz

SW – KC – universal SW

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SW – parts

The client application allows: The display of measured and calculated data stored in the system in graph and table formUse of support tools for the presentation of data and creation of reportsUse of predefined methods of processing measured data to obtain new data (calculated data)Define own methods of processing measured or calculated data with the possibility of their recurrenceExport measured and calculated data and their reports in the form of graph or data outputs

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SW – data

Source of data:Data measured by an electrometer Measurements performed by a grid analyzer Measurements imported to the headquarters in the form of XML files

SW contains a predefined set of variable quantities that it understandsSW automatically compares the set of incoming variables with the predefined relevant set Automatically enters the variables, which are available in data sources, into the system

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SW – Measurement screen, view

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SW – Admin. building – power distribution

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SW – Admin. building, course of power

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Reality

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How do losses change?

2321

23

22

21

23

22

21

2

2

)()).((

PPPIIIUUU

PSk r

z

min2121 )( JZZPSPS PkkPPE.g. increasing the P/S from the value of 0.9 to the value of 0.96 , means a reduction of the actual losses by at least 15% of the size of possible losses

The energy distribution enterprise at the level of LV and HV, distributes 7 TWh of electricity. The measured average coefficient P/S is 0.9. Based on data from the Annual Report, flat overall losses total 8.2%. What would the losses be that could be technically feasible to eliminate?

Let’s calculate the flat rate of technical losses of 5% of the invoiced (active) energy, i.e. 350 GWh. If we improve the average coefficient P/S to 0.96, losses will be reduced by 15% of min. losses, i.e. by 52.5 GWh.

(the said amount of GWh represents the consumption of more than 10,000households...).

Efficiency and losses – example

SW – formulas

They represent a major part of the systemThey come from a lot of work and own studies Only three formulas are always available, which can be used with the given data

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SW – own formulas

Own formulas can be defined

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SW – other functions

Export results, data

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SW – export data, U output

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TopologyEnables the evaluation of measurements not within individual measurement points, but as a set of measurements from various measurement points, which form an integrated part of the grid –they have their own topology..

SW allows multiple ways of processing data taking into account the topology of the grid

Balanced (above the group of multiple measurement points)Differential (comparison of twomeasurement points against each other)

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Battle to increase PF

Phase shift between u and i – compensation

Higher harmonics – filtration

Asymmetry – reconfiguration of grid

Other method - possibly?

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Y node in one phase

Outgoing currents are i1 (t) a i2 (t) (immediate value), incoming current i (t)Other variables: Pi – active power of relevant branch, Ii –RMS current, Si – apparent power, PFi – power factor of relevant branchThe node is connected to voltage u (t)

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i1(t)i (t)

i2(t)u (t)

L

N

Y node in one phase

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The resulting power is given as the sum of two others in thenode. Yes, but…

)()()( 21 tititi

)()(2)()()( 2122

21

2 tititititi

We will exponentiate both sides

We apply the mean value operator

TTTTdttiti

Tdtti

Tdtti

Tdtti

T 0 210

220

21

2

0)()(2)(1)(1)(1

Y node in one phase

We will receive

The apparent power will be (or quadrate)

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Tdttiti

TIII

0 2122

21

2 )()(2

Tdttiti

TUSSS

0 21

222

21

2 )()(2

Y node in one phase

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SPPF

2

0 2122

21

2 )()(2

P

dttitiT

IIU

z

T

k

Hodnota I I1 I2spolo ný reg.výkonu úsporka

U [V] 245,41 245,39 245,43I [A] 0,24 0,18 0,15P [W] 42,7 20,2 22,3Q 1 [var] 20 20 -10S [VA] 58,90 44,17 36,81PF 0,72 0,46 0,61kz 1,90 4,78 2,73THD [%] 48,7 65,9 73,1

Y - measurement

Measurements according to the Y figure: 3 watt meters, 3 amperemeters, 3x PF measurement…we measure using only one electrometer LZQJ-XC !

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THANK YOU FOR YOUR ATTENTION