LV Voltage Optimisation for Losses Mitigation...Variable Total Harmonic Distortion (THD) on current...

LV Voltage Optimisation for Losses Mitigation Analysis of powerPerfector iQ PNDC Trial

LV Voltage Optimisation for Losses Mitigation

Analysis of powerPerfector iQ PNDC Trial

UK Power Networks (Operations) Limited. Registered in England and Wales. Registered No. 3870728. Registered Office: Newington House, 237 Southwark Bridge Road, London, SE1 6NP Page 2

1 Summary As part of our Losses Discretionary Reward tranche 1 submission, UK Power Networks tested the

powerPerfector iQ power optimisation device at the Power Networks Demonstration Centre (PNDC)

facility to determine its ability to mitigate losses on LV electricity distribution networks. We found

that the powerPerfector iQ device is capable of significant losses reduction by virtue of its ability to

reduce and precisely target system volts. Loss reduction figures of 17% were achieved on the PNDC

trial network at UK average voltage levels of 242 volts. With higher voltages, loss reductions of up to

20% were achieved, or up to 11 kW in loss reduction on 350 amp loads. In this document the

methodology and results of our tests are presented, followed by analysis and discussion of potential

future projects, and finally a partial Cost Benefit Analysis (CBA) is presented, analysing the potential

upside value of the device in a distribution network context.

2 Contents 1 Summary ......................................................................................................................................... 1

2 Contents .......................................................................................................................................... 2

3 Introduction .................................................................................................................................... 3

4 powerPerfector iQ Testing .............................................................................................................. 4

4.1 Testing Methodology .............................................................................................................. 4

4.2 Testing Analysis ....................................................................................................................... 6

powerPerfector iQ Efficiency .......................................................................................... 6

Losses Improvement ....................................................................................................... 7

Energy Efficiency Improvement .................................................................................... 12

THD Improvement ......................................................................................................... 13

Voltage Imbalance ........................................................................................................ 13

4.3 Testing Conclusions ............................................................................................................... 14

5 powerPerfector iQ Use Case Analysis ........................................................................................... 14

5.1 Network Losses ..................................................................................................................... 14

5.2 Energy Efficiency ................................................................................................................... 14

5.3 Distribution System Operator ............................................................................................... 15

6 Cost Benefit Analysis ..................................................................................................................... 15

7 Conclusions ................................................................................................................................... 16

8 References .................................................................................................................................... 17




3 Introduction As part of our Losses Discretionary Reward (LDR) tranche 1 submission, UK Power Networks

committed to using the Power Networks Demonstration Centre (PNDC) to investigate innovative

approaches for reducing network losses. The PNDC is a test distribution network affiliated with the

University of Strathclyde. Amongst other facilities, it has a trial LV network, 11kV network, load

banks, and triphase impedance simulator.

As part of a separate commitment within our LDR tranche 1 submission, we undertook a series of

network modelling exercises with Imperial College London (ICL). These concluded that three key

losses drivers are: poor power factor, load imbalance, and high voltage. This work also determined

that 75% of all technical network losses are on the HV (11kV) and LV networks. We engaged in a

search for technologies and approaches that would improve these network characteristics so as to

reduce losses on these network voltages. ICL also identified issues with a small proportion of lengthy

circuits which were heavily loaded at the remote end.

ICL informed us of the existence of the powerPerfector iQ (iESCO, 2016): a device that addresses

multiple losses drivers simultaneously, as well as reducing harmonics. The powerPerfector iQ is a

power optimisation device. It was developed by iESCO Ltd to reduce LV voltages on customer

premises. By reducing the voltage level from the typical UK average of 242 V down to around 220 V,

customer appliances on average run more efficiently. This is because most appliances are designed

and optimised for lower voltage levels than exist in the UK.

Appliances draw different levels of load depending on their response to differing levels of voltage,

with different appliances being categorised in terms of a ZIP load model, where Z means constant

impedance, I means constant current, and P means constant power. With Constant impedance loads

a reduction in applied voltage will lead to a proportional reduction in drawn current (and hence a

more than proportional reduction in network losses). Constant current loads will draw a lower level

of power when voltage is reduced. Constant power loads will draw increased levels of current when

voltage drops. All loads on the distribution network will be some mix of these three types.

By reducing voltage powerPerfector iQ will typically result in a reduction in observed load current,

and hence in losses on the distribution network. powerPerfector iQ is an established technology on

the customer-side of the meter that has been installed on the premises of many local authorities,

major retailers, factories, and government offices – including the offices of the UK’s energy markets

regulator Ofgem.

Following ICL’s advice, we chose to test the powerPerfector iQ at the PNDC facility. This report

describes the methodology of these tests and our conclusions. It also proposes future work and

presents the results of a partial1 Cost Benefit Analysis (CBA) of rolling out the powerPerfector iQ or

similar technologies on the distribution network.

1 The partial nature of the CBA reflects the fact we do not yet have full understanding of the total costs of purchase and installation of the powerPerfector iQ on the distribution network. Gaining this information is a driver of the proposed distribution trial project.




4 powerPerfector iQ Testing

4.1 Testing Methodology Our testing methodology had two objectives:

Validate the manufacturer’s claimed performance, efficiency, and capabilities of the

powerPerfector iQ device.

Provide a basis for estimating the potential benefits of deploying powerPerfector iQ on the

LV distribution network.

In order to achieve the second objective we chose to deploy the PNDC’s extensive LV network,

generators, triphase load simulator, and load banks to simulate a set of ‘test networks’. These test

networks were configured by changing the loss-driver parameters over a range and observing the

impact these had on network losses, and then comparing this with the network losses that appeared

when the powerPerfector iQ was in operation.

Our testing methodology is laid out in detail in our test plan (UK Power Networks, 2017). Briefly, we

took the following parameters of interest, and applied a set of voltage profiles, based on the range

of voltages that we might typically expect to see on the LV network. The parameters were then set

at varying levels. The parameters and their levels are listed as follows:

Variable cable length (600 m, 1200 m, 3000 m)

Variable load level (150 amps per phase (30% of powerPerfector iQ rating), 250 amps per

phase, 300 amps per phase, 350 amps per phase)

Variable power factor (0.8, 0.85, 0.95, 1.00)

Variable output voltage (222 V, 225 V, 228 V, 230 V)2

Variable Total Harmonic Distortion (THD) on current and voltage (3rd harmonic, 5th harmonic,

and 7th harmonic at 0%, 2.5%, 5%, 7%, and equal mix of 2.5%, 5%, and 7%3)

The input voltage levels were specified as follows. In each case an oscillation was introduced in order

to reflect the fact that real-world voltage levels are often variable and subject to variation over time.

Nominal voltage (230 V)

Nominal voltage +5% (242 V)

Nominal voltage +10% (253 V)

Nominal voltage -3% (216 V)

Nominal imbalance

Nominal +5% imbalance

The input voltages and imbalance were generated by another powerPerfector device, which is used

as an LV/LV transformer. Power is provided by a 5 MVA generator on the PNDC 11kV network.

Measurements are taken by Power Quality Analysers (PQA) on either side of the powerPerfector iQ

2 This is to check the powerPerfector iQ is capable of setting the output voltage with a sufficiently high level of precision and stability. 3 This means that we applied an equal amount of 3rd harmonic, 5th harmonic, and 7th harmonic sufficient to produce a total THD of each of the indicated percentage values.




device under test, and a further PQA is placed next to the dummy load at the end of the mock

network impedance. Details are shown in Figure 1.

Figure 1: Test network SLD

The network impedance was made up of three mock impedances of 0.117+j0.014 ohms each. There

were also 185 mm2 aluminium LV cables between different sections of the LV test circuit.

As an example of the input and desired output profiles, the profile for the nominal voltage (230 V) is

shown in Figure 2. The profile for the nominal imbalance is shown in Figure 3.

Figure 2: Input voltage profile and expected output voltage profile for the powerPerfector iQ.

215.00

220.00

225.00

230.00

235.00

240.00

245.00

250.00

255.00

Vo

tage

(vo

lts)

iQ Input (Ph-N) Expected iQ Output




Figure 3: Input voltage profile and expected output profile for nominal voltage +2%, variance with L2 imbalance >2.5%, L3 imbalance >5%, and expected output voltage profile for the powerPerfector iQ.

4.2 Testing Analysis The results of the voltage studies show that the powerPerfector iQ was capable of driving voltage to

the desired set level within less than a second, and successfully held it stable despite intentional

changes in the input voltage. These intentional step changes induce small changes in the output of

the powerPerfector iQ, but are within tolerances (i.e. do not push outside the statutory limits,

assuming the input voltage is already well within the limits) and are of only a short duration

(approximately half a second) and magnitude (approximately 1 volt) relative to the targeted output.

powerPerfector iQ Efficiency

The manufacturers of the powerPerfector iQ claim a peak efficiency of over 99% (iESCO, 2016). In

our tests, depending on the input parameters and test scenario, we derived efficiency

measurements of between 98.89% and 99.91%. This is broadly in line with the manufacturer’s

claims.

Our tests suggest that use of the powerPerfector iQ would not represent a significant new source of

losses, especially in comparison with the magnitude of the losses reductions that can be achieved by

deploying the powerPerfector iQ on the distribution network.

The efficiency of the powerPerfector iQ device is shown in Figure 4 below for different levels of

loading at average UK voltage levels (Ministry of Defence, 2010). As can be seen in Figure 4, there

appears to be no systematic relationship between loading and efficiency, at least at these levels of

loading4.

4 Note that this used a 500 amp unit and our maximum loading was 350 amps.

215

220

225

230

235

240

245

250

255

Vo

ltag

e (v

olt

s)

iQ L1 Input iQ L2 Input iQ L3 Input Expected iQ Ouput




Figure 4: PowerPerfector iQ efficiency at average UK voltage (242 volts)

Losses Improvement

The methodology for calculating the losses improvement achieved by the powerPerfector iQ is

described as follows.

Each test scenario (as described above) involved setting up the test rig with the parameters of

interest set at the desired levels. Measurements were taken at each of the points shown in Figure 1

to provide a baseline of system performance. The powerPerfector iQ was then energised. The input

voltage was then adjusted in line with the specified profile. Again, measurements were taken with

the powerPerfector iQ energised.

To determine the relative magnitude of losses, we needed to take the “difference in differences” as

illustrated in Figure 5 below. The network losses are the difference between the output PQA active

power measurement and the load PQA active power measurement, that is, they are the losses

across the network impedance shown in Figure 1. When the powerPerfector iQ is energised the

difference between the output PQA active power measurement and the load PQA active power

measurement changes. This change represents the losses improvement attributable to the

powerPerfector iQ. Therefore, the losses improvement is the difference between A and B in Figure 5.

98.90%

99.00%

99.10%

99.20%

99.30%

99.40%

99.50%

99.60%

99.70%

99.80%

99.90%

100.00%

Effi

cien

cy (

%)

Loading Level (amps)

PPiQ Efficiency at Average UK Voltage




Figure 5: Meaning of test levels

In the subsequent sections of this document, losses are presented in percentage terms of loss

improvement, i.e. a reduction of loss from 29.6 kW with the powerPerfector iQ deactivated to 24.5

kW with the powerPerfector iQ activated represents a reduction in losses of (29.6 – 24.5)/29.6 =

17%. We also present losses in absolute terms for the purposes of developing a Cost Benefit Analysis

(CBA). This CBA uses the standard Ofgem CBA methodology, and values losses at £48.42/MWh of

loss mitigation with a discount factor of 3.5%.

4.2.2.1 Variable Cable Length

To analyse the powerPerfector iQ’s impact the load banks were connected via varying network

impedances, each equivalent to a particular length of LV cable. The cable lengths used are shown in

Table 1. The network impedances are roughly equivalent to 185 mm2 waveform aluminium (UK

Power Networks, 2015).

Table 1: Cable lengths and equivalent network impedances

Cable Length (metres) Impedance (ohms)

600 0.117 + j0.014

1200 0.234 + j0.028

1800 0.351 + j0.042

The results of the cable length losses improvements are shown in Figure 6 below. As can be

observed, the higher the input voltage profile the greater the reduction in losses. This reflects the

fact that the load banks present a constant impedance load to the device. Thus, a reduction in

voltage leads to a reduction in current, which in turn leads to a reduction in I2R losses in the cable.




Figure 6: Losses improvement for variable cable lengths and varying input voltage profiles

4.2.2.2 Variable Load Level

To analyse the power Perfector iQ’s impact on losses with variable load levels, we set the load banks

to a set of different levels and observed the losses across the network impedance. The load levels

used are shown in Table 2 below.

Table 2: Load levels in amps per phase

Load levels (amps per phase) Load level as a % of PowerPerfector iQ rating

150 30%

250 50%

300 60%

350 70%

The results of the loading level loss improvements are shown in Figure 7 and Figure 8 below.

0%

5%

10%

15%

20%

25%

600 m 1200 m 1800 m

Loss

Imp

rove

men

t (%

)

Losses Improvement for Variable Cable Length

230 volts 242 volts 253 volts




Figure 7: Losses improvement for variable loading level and varying input voltage profiles, % of loading

Figure 8: Losses improvement for variable loading level and varying input load profiles, in active power

4.2.2.3 Variable Power Factor

To analyse the powerPerfector iQ’s impact on power factor, and consequent impact on losses, the

load banks were set so as to present a load with a power factor of 0.8, 0.85, 0.9, and 1.00. The

0%

5%

10%

15%

20%

25%

150 250 300 350

Loss

Imp

rove

men

t (%

)

Loading Level (amps per phase)

Loss Improvement for Variable Load Level

220 volts 230 volts 242 volts 253 volts

0

2

4

6

8

10

12

14

150 250 300 350

Loss

es (

kW)


Loss Improvement for Variable Load Level (kW)





respective power factors were achieved by setting the load banks to total powers shown in Table 3

below.

Table 3: Load bank power settings to achieve targeted power factor

Targeted Power Factor Total Load Bank Power Setting (kW)

0.8 140

0.85 148.75

0.95 166.25

1.00 175

Figure 9: Loss reduction achieved by powerPerfector iQ for various power factors.

The results suggest no significant impact on power factor attributable to the powerPerfector iQ.

Moreover these results suggests that poor power factor in and of itself reduces the potential for loss

mitigation using Conservation Voltage Reduction (CVR). This is in part a result of the nature of the

applied testing regime: to achieve the desired power factor we reduced the level of current drawn

by a variable power factor load bank. The power Perfector iQ then dropped volts. The result is that

the power drawn by the load bank reduced, as did the current, and as did the I2R losses.

4.2.2.4 Variable Output Voltage

The powerPerfector iQ achieved extremely good performance in terms of its ability to control and

adjust voltage on the output. The targeted output was achieved very precisely and within less than 1

volt of the target output. The target output was achieved within less than half a second.

4.2.2.5 Variable Total Harmonic Distortion Improvement

To investigate the impact of the powerPerfector iQ on voltage and current Total Harmonic Distortion

(THD) varying levels of THD in the voltage and current waveform were applied as per Table 4.




Table 4: THD values

THD (both voltage and current) Harmonics

0% -

2.5% All 3rd, All 5th, All 7th, Mixed (3rd, 5th, 7th)

5% All 3rd, All 5th, All 7th, Mixed (3rd, 5th, 7th)

7% All 3rd, All 5th, All 7th, Mixed (3rd, 5th, 7th)

Energy Efficiency Improvement

The load banks used in our tests were simple reactive loads with constant impedance. This means

the reduction in voltage led to a proportional reduction in current (and hence a greater-than

proportional reduction in losses). In reality, customer loads will typically respond to the change in

voltage levels in a combination of three ways:

Constant impedance (Z) loads will reduce proportionately to the reduction in voltage

Constant current (I) loads will draw less power in response to the reduction in voltage

Constant power (P) loads will increase in response to a reduction in voltage

Because we do not have a clear idea of the empirical load makeup on our distribution network, and

because the makeup of load is changing all the time as different appliances are turned on and off,

we cannot generalise as to the energy efficiency improvement attributable to Conservation Voltage

Optimisation (CVO) of this type. However, studies (Western Power Distribution, 2016) have shown

that voltage reductions typically lead to reductions in load, implying that loads are predominantly of

the constant impedance (Z) type.

The impact of voltage reduction on the test network for various loading levels is shown in Figure 10

below. As can be seen in the chart, for a load level of 350 amps, there was a reduction of 30 kW

associated with reducing voltage from the UK average to the target output voltage of 220 volts.




Figure 10: Load reduction by voltage reduction for variable load level

THD Improvement

No significant difference in losses was discovered for varying levels of either current or voltage THD.

This confirms the ICL studies that suggest current and voltage harmonic distortion is not a significant

driver of network losses.

There was a slight reduction (average: -0.2%) in voltage THD across all scenarios. There was no

observed reduction in current THD. Interestingly, the impact of the powerPerfector seemed to filter

out 3rd and 7th harmonics but not 5th harmonic.

Voltage Imbalance

The powerPerfector iQ can improve voltage imbalance caused by load imbalance. The results of

applying voltage imbalance via the separate 750 kVA powerPerfector shown in Figure 1 are shown in

Figure 11 below. The definition of imbalance is as per section 5.7 of (British Standards Institute,

2017). As can be seen in Figure 11 the powerPerfector iQ has a significant positive impact on

imbalance.

0

5

10

15

20

25

30

35

40

150 250 300 350

Load

Red

uct

ion

(kW

)


Load Reduction by Voltage Reduction for Variable Load Level





Figure 11: Unbalance results showing imbalance before and after powerPerfector iQ energisation

4.3 Testing Conclusions It is concluded that the powerPerfector iQ offers significant potential for high-precision, high-

responsivity LV voltage optimisation for losses management. Moreover, there are a number of other

use-cases for the powerPerfector iQ and similar devices. These are discussed in more detail in the

following sections.

5 powerPerfector iQ Use Case Analysis

5.1 Network Losses As expected, the powerPerfector iQ caused a reduction in network losses. This was achieved by

reducing the voltage presented to the test load bank. In the UK voltages are generally recognised to

be “too high” on average. Whilst DNOs maintain LV levels between the statutory bands (i.e. 230

volts +10%, -6%), the legacy of older standard voltage levels means that average voltages presented

to LV customers are typically around 242 volts. Most appliances, on the other hand, are

manufactured and optimised for lower voltage levels.

This means that many customer appliances operate at a voltage level higher than that which

optimises their energy efficiency, and draw more power than necessary to function. Moreover, in

order to supply this extra power the network losses are higher than would otherwise be the case,

and higher levels of generation are required than necessary.

Our tests confirmed that the powerPerfector iQ was capable of both raising and lowering volts to a

desired set point. The ability to monitor and control voltage in a real-time environment is an exciting

potential benefit of the powerPerfector iQ. Because of the dynamic and varying nature of real-world

customer loads, traditional CVR methods are insufficient. Simply dropping the volts on the primary

transformer tap-changers is a crude approach, albeit one that has been shown to successfully reduce

observed load (Western Power Distribution, 2016).

5.2 Energy Efficiency The powerPerfector iQ was originally developed to improve the energy efficiency of large buildings.

This use case remains the biggest potential benefit of the power Perfector iQ in economic terms.




Interestingly and challengingly, it is not clear how the obvious economic benefit of CVR (i.e. reducing

the LV presented to the customer the lower range of the acceptable limit) would be claimed by the

DNO.

In general, reducing voltage will reduce load on the distribution network. This is a well-understood

phenomenon and is used as part of the emergency load shedding procedures in the Grid Code.

5.3 Distribution System Operator There is extensive discussion in (Imperial College London, 2013) on the value of voltage control

enabled demand response technologies to the GB electricity system. As part of UK Power Networks’

vision to become a Distribution System Operator (DSO), we aim to extend our abilities to facilitate

the provision of DER (Distributed Energy Resources) to the wider grid. Voltage control represents

one such possible DER for the system operator to call on if required.

powerPerfector iQ is capable of changing volts in a timespan of less than half a second, and holding

volts at a precise level. As such it represents one possible implementation of voltage control-enabled

frequency response. iESCO Ltd. are currently engaged in a research project with National Grid to

investigate the potential applications of the device in the DER arena.

As well as the potential for frequency response, the powerPerfector iQ can enhance UK Power

Networks’ DSO capabilities by providing a means to facilitate connection of solar panels and electric

vehicles. With increased penetration of solar panels, and increased electrical loading attributable to

the take-up of electric vehicles, heat pumps, and other low-carbon technologies, there is an

increasing drive by Ofgem to develop cost-effective means of managing power flows on the

distribution network, as well as mitigating losses. The powerPerfector iQ represents one such tool.

6 Cost Benefit Analysis The input assumptions for the CBA are shown in Table 5 below. The results of the standard Ofgem

CBA methodology applied to installation of the powerPerfector iQ in a standard distribution. Note

that this CBA is presented without install costs and maintenance costs. It is intended to reflect a

“typical” feeder and ignores nonlinear effects of load profiles on network losses and loading. As such

it is taken as indication of approximate values using the outputs of the PNDC trial as a basis. It is

proposed that further analytical work be undertaken to refine these estimates.




Table 5: CBA and Assumptions

7 Conclusions We draw the following conclusions with a high degree of confidence:

The powerPerfector iQ device functions in line with its stated efficiencies and capabilities

There is considerable scope for further investigation of the potential benefits of deploying

this technology on the distribution network

The device offers a number of potential use-cases that drive DNO to DSO benefits, including

voltage control, facilitation of EV connection, and frequency response services.

As part of our LDR tranche 2 submission, we intend to continue to work with our industrial partners

at iESCO, and our academic partners at Imperial College, to develop this technology and adapt it for

use on the distribution network. Our trial will investigate the potential benefits of installing a

powerPerfector iQ on the distribution network. We will take the opportunity to measure and

quantify the potential benefits of conservation voltage reduction on representative LV feeders, and

analyse the potential for real-time control algorithms to continuously optimise voltage in response

to changing load type.

Input Assumptions of powerPerfector iQ CBA Value

Average Loading of Feeder (amps): 350

Minimum Customer Voltage (volts): 242

Average Losses Delta (kW): 9.62

Total Average Annual Losses Delta (kWh): 84,271.20

Ofgem Value of Losses (£): 48.42£

Total Annual Value of Losses (£): 4,080.41£

Discount Rate: 3.5%

Regulatory Period (years): 8

NPV of Losses: 28,048.57£

Average Load Delta (kW): 30

Cost of Electricity (£/kWh): 0.1437£

Total Annual Consumption Delta (kWh): 262,800

Total Annual Value of Consumption Delta (£): 37,764.36£

NPV of Consumption Delta (£): 259,590.53£




8 References British Standards Institute. (2017, 02 28). BS EN 61000-4-30:2015 Part 4-30.

iESCO. (2016, 11 16). powerPerfector iQ Specification Sheet. iESCO.

Imperial College London. (2013, 09). Assessment of the Role and Value of Voltage Control-Enabled

Demand Response Technologies in Future GB Electricity System.

Imperial College London. (2017). Quantifying Distribution Network Losses - Informing Loss Reduction

Strategies. Retrieved from UK Power Networks Losses Website:

http://www.ukpowernetworks.co.uk/losses/static/pdfs/quantifying-distribution-network-

losses-informing-loss-reduction-strategies.5272e56.pdf

Ministry of Defence. (2010, 01 11). Justifying and Delivering Voltage Optimisation on the MOD

Estate. Retrieved from GOV.UK:

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/33611/pg

01_10.pdf

UK Power Networks. (2015, 09 04). EDS 02-0033 LV Waveform Mains Cable Ratings. Retrieved from

https://library.ukpowernetworks.co.uk/library/en/g81/Design_and_Planning/Cables/EDS+0

2-0033+LV+Waveform+Mains+Cable+Ratings.pdf

UK Power Networks. (2017, 09 13). pP iQ UKPN Master Test Plan 2017-09-13 FINAL.

Western Power Distribution. (2016, 06). Innovation Projects - Voltage Reduction Analysis. Retrieved

from Western Power Distribution:

https://www.westernpower.co.uk/Innovation/Projects/Closed-Projects/Voltage-Reduction-

Analysis.aspx

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