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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
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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
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