Line Conditioners

Generally

The name conditioner, the word of French origin is used in Anglo-American practice and literature and it means equipment, which arranges and adapts certain quantities to standard or desirable conditions and requirements. It is known more in consequence with temperature treatment and the damp of surrounding air.

Line conditioner is equipment working on principle of serial compensation of mains voltage changes by means of series connection transformers supplied by a converter with pulse width modulation.

This equipment works as output voltage regulator for public electricity network of distribution in wide span of input voltage with independent stabilizing effect of separate phases, very fast effect and short time drops compensation.

Conditioner processes only the part of the output that is necessary for completion of the deficit caused by drops on the mains or for setting the consumption at ease.

Line conditioner EAFS072 outlet part and outlet partfig. 1 Line conditioner EAFS072 outlet part and outlet part

 

Variable Symbol Unit EAFS018 EAFS036 EAFS072
Throughput Power SN kVA 18 36 72
Converter Output SM kVA 3,6 7,2 14,4
Nominal Voltage Un V 3 x 230 / 400
Nominal Frequency f Hz 50
Input Voltage Fluctuation D uvst %(V) +10 (253), –20 (184)
Output Voltage Fluctuation D uvýst % +10 (253), –5 (218)
Output Current I2 A 26 52 104
Maximum Input Current I1max I1max A 32 63 125
Converter Current IM A 6 11 20
Overload 1h % 10
Overload 1min % 30
Overload 1s % 100
DC Link Voltage Max. Umax V 594
DC Link Voltage Min. Umin V 430
Efficiency h % > 95
Transformer Turns Ratio p - 6
Converter Circuit Protection A 10 gR 16 gR 25 gR
Recommended Serial Protection A 50 gG 80 gG 160 gG
Additional Protection A 32 gG 63 gG 125 gG
Short-Circuit Current of Network Ik kA max 1,5

 

Box

The conditioner itself together with filter and auxiliary circuits is located in steel sheet box of SVS-IZK series with increased coverage IP54 with outlet chimneys and ventilation grid (coverage IP54). The box is side-mounted to the pillar and it is supported by standard console used for boxes of the type SVS-IZK. Inlet and outlet cable will be led in through the bottom of the box through the bushings.

The conditioner has following dimensions:

Height: 1200 mm
Width: 1050 mm
Depth: 600 mm

 

Connection of EASF… to the LV distribution network

alinkk1 enfig. 2 Příklad připojení kondicionéru k rozvodnému vedení

 

Electric energy quality improvement

Majority of regulations and standards concern electric energy quality defines following parameters:

  • Deviations from nominal voltage
  • Interruption and expressive voltage drops
  • Cyclic voltage fluctuation (flicker)
  • Symmetry of three - phase system
  • Harmonic frequencies volume
  • Signal frequencies level (ripple control)

Conditioner is equipment which can provide basic parameters of the electric energy quality by elimination of some interference influences in the supply line. Each type and each kind of conditional equipment describes parameters mentioned above by its own specific way. The more they are ensured the more complicated, the more expensive and less applicable in public network the equipment is.

For line conditioners are following minimal concrete values required:

  • Balancing of inlet voltage drop up to 20 % (exception up to 30 %)
  • Keeping voltage on the output in limits 5 %
  • Speed of acting as high as possible
  • Time lag less than 0.1 s - slow regulation - voltage regulator
  • Time lag less than 0.01 s - fast regulation - will remove flicker

 

Conditioner principle

Chart of Line conditioner Connectionfig. 3 Chart of Line conditioner Connection

 

G – line source (e.g.. transformer station
GK – line conditioner (converter part)
I1 – circuit without load
I2 – circuit into the converter of the conditioner
I3 – circuit into the primary TS (I3 = I1 / p)
U0 - line source voltage
U1- conditioner inlet voltage
U2 - conditioner output voltage (U2 = U0)
TS - serial transformer of conditioner
Z1 – impedance of the mains (line)
Z2 – impedance of the load

It is always supposed when we are thinking about the volume of drops that by the source of energy, i.e. by HV junction point or by the near end of the LV line parameters (U0) are suitable and insufficiency (voltage drops etc.) are caused by activities of power consumers.

Voltage drops are created as is well known by impedance drops Z1, Z1 that is accurately more on the line resistance RV and on line reactance XV. Current flow presents according to the character of Z2 active component IR and reactive component IX, which has mostly inductive character. With certain simplifying we can write for total drop:

vzorec11

From classical network theory and also from some measurement can be briefly judged that consumption of considered soft LV networks contains two components:

  • Basic that changes slowly, largely of active character
  • Temporary that changes fast, largely of inductive character

LV line character can be various, outside lines and also cable lines are of cross section from 35 to 75 mm2 and corresponding wire resistance is 0,3 to 1,5 W. Reactance of outside LV lines is slightly dependant on the cross section and is approximately 0,3 W. When line loading is approximately symmetric, only drops of outer conductors are applied. The drop in unloaded centre conductor (PEN) is not significant. When loading of phases is considerably non symmetric, approximately the same drop volume is applied on centre conductor. For equal current the voltage drop can be double.

With suitable power consumers distribution and connection it is possible to keep consumption symmetry and so that acceptable drops for basic element of consumption. Fast variable element (starts-up of motors, electric kettles, microwave ovens, e.g.) is more under control of random fluctuation and summations, so it is practically impossible to reach symmetrical consumption. Drops on centre conductor have indifferent phase generally.

Suitable illustration of relationships is demonstrated on Fig. 4. Here is described relation between phase voltage and instantaneous consumption in typical place considered after conditioner installation. The expressive linear dependency, which can also be calculated, is assigned the dissipation caused by variable power factor of the load and current variation in other phase conductors.

Relation between voltage drop and load current (at the place of supposed installation of conditioner)fig. 4 Relation between voltage drop and load current (at the place of supposed installation of conditioner)

 

If the voltage changes repeat more or less regularly, even in low limits, sensitivity of consumers on this subjective perception of fluctuation in association with general electric lightning (bulb) is growing (flickering). In such cases acting speed of conditioner influence is positively applied as high as possible. Maximal sensitivity of human eye is stated within frequency fluctuation 1 to 10 Hz.

The aim of output conditioner voltage is to reach cross hatched area on Fig. 3. Crossed lining indicates upper and bottom limit of effective voltage value fluctuation permitted by standards. Regime of conditioner as stated before can be divided into two control way:

  • Classical regulation on effective voltage value in each period with delay, so that additional flicker will not occur.
  • Fast regulation on reference sine curve in every moment, it means basically serial active filter. This regulation enables also to remove deformation output, or harmonic voltage elimination.

Second way of regulation is more exacting and it supposes signal processor utilization, and utilization of special mathematical tool. With second type of regulation it is necessary to exclude mathematically useful signals of ripple control so that these would not been influenced by conditioner activities.

Utilization of conditioners with pulse width modulation

Pulse width modulation (PWM) is today current way of regulation of electric energy flow by means of fast switching - on of circuits by powerful transistors IGBT. On this principle operate almost all of new converters for drives, power supply units (UPS) and other electrical appliances.

Conditioners are based on the principle of processing only the part of the output, which is necessary to supply deficit, made by drops on the line or necessary for suppression of consumption on Fig. 4.

General Block diagram of line conditionerfig. 5 General Block diagram of line conditioner

 

The line ends-up at the conditioner input with soft characteristic. Between input and output clamps is lined - up secondary winding of additional serial transformer. Primary winding is supplied from converter system. Block diagram is according to Fig. 4 composed of:

  • Input protective circuit and RFI filter
  • Rectifier
  • Accumulation capacitor battery
  • Transistor alternator PWM
  • Inlet protective circuit, of these functions:
    • Prevention of PWM connecting frequency penetration into output of conditioner
    • Interference elimination in high frequency zone of communication
    • Liquidation of dangerous bias voltage
  • Short circuiting of serial transformers primary winding TS in case of defect state of equipment of desire origin or short circuit on the line
  • Control subsystem composed of microprocessor unit is connected for restart or setting up parameters (terminal TERM401)

Conditioner possibilities

Conditioner is not the source of energy and that is why the balancing of input voltage has its own physical limit. Voltage drop -30 % can be considered, regardless to high losses associated, as the limit of serial compensation of line drops. Its drop supposes that output necessary in serial circuit see Figure 4 (Alternator PWM + serial transformer) is to be drawn from parallel circuit (Input circuit + rectifier) and thus the voltage drop in the place of connection will be deeper. Highest output, which can be taken from, the line with impedance Z1 taken away by power consumer with impedance Z2 is in condition of Z1 = Z2. This corresponds to voltage drop to 50 %. The same condition occurs when natural drops over 30 % are conditioned which results in collapse of the system.

Utilization of conditioner energy for power system

In the Czech Republic exists a lot of LV line run-outs that cannot give a guarantee of electricity in quality according to new standards and requirements. Their eventual reconstruction would be impossible because of time consumption and high investment costs. That's why the first series of line conditioners was developed.

Because of the device price in serial production has application of conditioner big advantages in comparison to reconstruction of the line, where in majority of cases strengthening of the LV line would not be sufficient and it would be necessary to provide more extensive reconstruction of the whole network.

Line conditioner output is presented as throughput power output, the output of converter is lower and it is about 20 % of throughput, see Tab. 1. For example line conditioner of 36 kVA output has converter output of 7.2 kVA. Regarding to the fact, that transistor converters are working with efficiency higher than 95%, then the power dissipation of the converter is about 300 W.

Line conditioner regulates effective voltage value in each following period, providing symmetry and removes flicking blinking (flicker). In very fast performance (active serial filter) it enables to remove deformation output (to smooth voltage curve) eventually to remove certain voltage harmonics. Further it enables to improve the balance of active and reactive power.

Line conditioner EAFS072 - supply, control and transducers partfig. 6 Line conditioner EAFS072 - supply, control and transducers part

 

Line conditioner's assembly EAFS036fig. 7 Line conditioner's assembly EAFS036

 

Results of measurements

During practical application of conditioner the basic measurement was done - before and after conditioner application. On Fig. 8 the course of effective voltage value in all three phases is depicted, in the point of the distribution line, which supplies a remote area. From the voltage waveform that is here illustrated in the time of several days is apparent that the fluctuation is high and in many cases reaches values under the standard limits permission.

After connection of line conditioner to the power supply the quality of electric energy was distinctively improved. On Fig. 9 is illustrated the voltage waveform in the same place after conditioner connection. The difference in supply is clear. There is a certain disadvantage of this type of conditioner there, that it is not able to regulate the voltage downwards. However, a presumption can be made, that using the conditioner will be just in places, where rather undervoltage than overvoltage occurs.

Waveform of effective voltage value before conditioner applicationfig. 8 Waveform of effective voltage value before conditioner application

 

Waveform of effective voltage value after conditioner applicationfig. 9 Waveform of effective voltage value after conditioner application

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