CA1083231A - Device for melting the icing by direct current on conductors of overhead power transmission line - Google Patents
Device for melting the icing by direct current on conductors of overhead power transmission lineInfo
- Publication number
- CA1083231A CA1083231A CA279,534A CA279534A CA1083231A CA 1083231 A CA1083231 A CA 1083231A CA 279534 A CA279534 A CA 279534A CA 1083231 A CA1083231 A CA 1083231A
- Authority
- CA
- Canada
- Prior art keywords
- rectifier
- current
- conductors
- filter
- lead
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Supply And Distribution Of Alternating Current (AREA)
Abstract
Abstract of the Disclosure A device for melting the icing by direct current on conductors of an overhead power transmission line, comprises a rectifier coupled during the ice melting period by its lead-out wires to the circuit between the disconnected conductor of the power transmission line and the ground wire, and a current filter set in resonance to the line to the commercial frequency, which is, for example, a capacitor bank connected in series to a reactor whose lead-out wires are connected in parallel to the direct-current voltage lead-out wires of said rectifier. The device can be used to melt the icing by direct current on conductors and cables of overhead power transmission lines within the voltage range from 110 to 220 kV and more.
Description
The present invention relates to electrical power engineering ancl, in particular, to a device for melting the icing by direct current and ean be employed for direct eurrent ice melting on conductors and cables of overhead power transmission lines.
There is known a device for melting the icing by direct current on conductors of overhead power transmission lines, including transformers coupled to the lines and grounded neutral wires, which eomprises a rectifier coupled to the heated eircuit made up of the phase (or conductor) disconneeted for ice melting and the grounding means of ter-minal substations. The voltage of t~e rectifier is several elasses below the voltage of the overhead power transmission line.
Iee melting by means of such devices presents no special technical difficulties in lines up to 35 kv, inclusive.
With higher voltage lines, up to 110-220 kv and more, ~ifficulties arise due to induced current and voltage ` of eommercial, that is power-cireuit, frequency from the still operating lines.
When conduetors of the ice melting line are dis-eonnected phase by phase, the line operates incompletely sinee only eonduetors of two phases remain operational, whereas conductors of the third phase are connected to the ice melting eircuit. EMF is indueed in the conductor connected ., . , ~ :
There is known a device for melting the icing by direct current on conductors of overhead power transmission lines, including transformers coupled to the lines and grounded neutral wires, which eomprises a rectifier coupled to the heated eircuit made up of the phase (or conductor) disconneeted for ice melting and the grounding means of ter-minal substations. The voltage of t~e rectifier is several elasses below the voltage of the overhead power transmission line.
Iee melting by means of such devices presents no special technical difficulties in lines up to 35 kv, inclusive.
With higher voltage lines, up to 110-220 kv and more, ~ifficulties arise due to induced current and voltage ` of eommercial, that is power-cireuit, frequency from the still operating lines.
When conduetors of the ice melting line are dis-eonnected phase by phase, the line operates incompletely sinee only eonduetors of two phases remain operational, whereas conductors of the third phase are connected to the ice melting eircuit. EMF is indueed in the conductor connected ., . , ~ :
- 2 -:
: : ~
.
~083Z31 to the ice melting circuit due to electromagnetic and electrostatic interferences of the two operating phases.
As a result current in the ice melting circuit comprises two distinct components: a permanent component caused by the rectifier EMF and an alternating component of the commercial (power-circuit) frequency caused by the induc-ed EMF.
The EMF and the variable component of the rectified current induced in the melting circuit of lines using up to 3S kv, inclusive, are not dangerous for 10 kv rectifiers employed for ice melting. For 110 kv lines and upwards these induced currents and voltages are dangerous and inadmissib-le for such rectifiers and their supply transformers. It becomes impossible to use 10-35 kv rectifier bridges and, sometimes, to melt the ice by means of phase by phase dis-connection of 110 kv lines and upwards.
Besides, in such devices overvoltages tend to appear on valves and insulation of the rectifier, when it is put in and out of operation.
When the ice melting circuit is connected (the recti-fier is put into operation), the induced alternating electro~
motive force whose polarity is the opposite of the valve conduction is applied to the lead-outs of the non-conduct-ing rectifier. The open circuit voltage reaches several tens of thousands volts, which can be dangerous both for the valves and for the insulation of the rectifier. The ;
_ 3 -::~A.
~, ..
., ", . .
1~)83Z31 other half-wave of the induced electromotive force coinci-des with the valve conduction direction and causes current pulsations in the ice melting circuit. In this case it is only the voltage drop on valves and connecting wires of the rectifier that is applied to the valves and insulation of the rectifier.
When the rectifier is put out of operation and its supply of alternating current is cut off, the rectified current drops to zero. All the induced electromotive force in the line conductor is then also applied to the valves and insulation of the rectifier, when its polarity is opposite to the valve conduction. This electromotive force is not dangerous for the installation in the other half-period.
As a result, large induced electromotive force, especi-ally when short circuit currents flow through the operating ~ . :
conductors of the line, requires that the number of series-connected valves in the rectifier arms be increased and its insulation be strengthened, that is the rectifier is to be made more powerful.
.~
When some phase is inoperative in the line during -ice melting, the alternating electromotive force induced in the disconnected conductor is the cause of the melting current variable component. In this case the rectified current of the rectifier is pulsing and the pulsation fre-quency is equal to the power-circuit frequency. Such pulsa-~' :'~
?
'. ;l ~A~
... . . . . .. . .
tions of the rectifier current result in direct components of the rectifier phase currents and, consequently, in the windings of the transformer supplying the rectifier. Direct current components lead to appearance of constant uncom-pensated magnetization fluxes, increase of the magnetization current and losses of power and energy in the steel of the rectifier supplying transformer.
Such magnetization becomes dangerous when the amplitude of the variable component in the rectified current does exceed the relative nominal transformer current by 5 or more percent but is within the limits of 5 or more percent rela-tive to nominal transformer current. The transformer cannot be allowed to operate under suàh conditions.
It is an object of this invention to eliminate the above listed drawbacks.
; Another object of this invention is to cut down over-voltages on the valves and insulation of the rectifier, which are produced when it is put in and out of operation.
~;! Yet another object of the invention is to prevent the ~-/ 20 alternating current of the ice melting circuit flowing through the rectifier.
This is achieved by that a commercial (power-line~
frequency current filter connected in parallel to the direct-current voltage lead-out wires of the rectifier.
The current filter is advisable to be made of at least one capacitor and at least one reactor connected in series.
., ,.
,, .
~ - 5 -;~; .
,:~
.
~ ~, `': iqA-108~ 31 Besides, in order to reduce the installed powers and, consequently, the price of the filter elements, it is advantageous to connect a discharger, e.g. a spark discharger, parallel to one of the filter elements, and in order to increase the reliability of operation to connect a switchgear device parallel to the filter, said device being turned on at the moment when said discharger operates.
The above listed objects are also achieved by connect-ing the filter reactor in series with the capacitor via the matching transformer.
It is also advantageous to connect at least one impedance~
between the lead-out wires of the current filter and the direct current lead-out of the rectifier.
The impedance can be connected either between the potential ungrounded lead-out of the rectifier and the junction point where the filter is joined to the line, or between the ; lead-out wire of the rectifier and the ground, or, when two impedances are used, one impedance can be connected between the potential lead-out of the rectifier and the current filter, 20 whereas the other impedance between the other lead-out of the rectifier and the second lead-out wire of the filter.
Reactors, conductors, cables of other overhead lines leading from the busbars of the substation where the rectifier is installed, or reactors of the current filter can be used as !
a current-limiting impedance.
., ' These objects are also achieved by connecting a commer-cial frequency voltage source whose phase and voltage can be regulated, in series into the circuit of the filter.
The most advantageous device which can be used as said voltage source is a single-phase transformer whose primary winding is connected in tandem with the neutral lead-out of the high-voltage winding of the transformer (autotrans-former) coupled to two operating phases of the heated line.
In order to more accurately compensate the alternating induced current in the direct current circuit of the rectifier it is advantageous to connect a matching complex load parallel to the secondary winding of said single-phase transformer, the parameters of said load being determined by the nature of the unbalance of the commercial frequency filter elements.
The disclosed device permits ice melting by means of phase-by-phase disconnection of conductors of the 110 kv line and upwards using industrially produced power rectifying ~; bridges of the 10 kv and 35 kv classes.
~; 20 The filter is installed parallel to the rectifier from the direct current side and this ensures a by-pass for the melting current variable component in the conductor.
As a result the rectifier current becomes more ideally smoothed and there are no direct components in the rectifier phase currents, whereas magnetization of the supply (anode) transformer is completely eliminated.
,. ~
~;
~.,, (~
. .
~,A; , Besides, the alternatiny induced electromotive force results in producing current in the circuit: disconnected conductor - current filter - ground - disconnected conductor.
Since the filter is tuned in resonance on the power-line frequency, the voltage drop thereupon caused by the current produced by the induced electromotive force is insignificant (equal to zero in an ideal case) and, consequently, over-voltages produced in the rectifier, when it is put into and out of operation, are eliminated.
In accordance with a specific embodiment, a device for melting icing by direct current through the conductors of an overhead power transmission line featuring transformers with grounded neutral wires connected thereto, comprises: a rectifier connected for the ice melting period by its direct-current voltage lead-out wires to at least one disconnected conductor of the power transmission line and a grounding circuit: and a commercial frequency circuit filter connected parallel to the direct-current voltage lead-outs of said rectifier.
The invention will now be described with reference to a specific embodiment thereof, taken in conjunction with the accompanying drawings, wherein:
Fig. 1 shows a schematic circuit diagram of an ice melting device featuring a commercial frequency filter coupled parallel to the direct-current voltage lead-outs of the rectifier:
Fig. 2 shows a similar device of Figure 1 and featuring a filter, whose one element is shunted by a discharger:
Fig. 3 shows a device of Figure 2, featuring an addition-al switchgear installation placed in parallel with the filter:
. .
.
~, - . : . . .- - -. .: . -. . .
108323~
Fig. 4 shows a device featuring a filter whose reactor is coupled via a matching transformer, Fig. 5 shows a device, wherein an impedance is connected between the ground and the direct-current voltage lead-out of the rectifier, Fig. 6 shows a device, wherein an impedance is connected between the potential direct-current voltage lead-out of the rectifier and the junction point where the filter is joined to the heated circuit, Fig. 7 shows a device featuring two current-limiting impedances connected in series with the rectifier from the side of the line and from the side of the ground.
Figs. 8 and 9 show devices, wherein impedances are reactors connected respectively between the ground and a pole of the rectifier, as well as between the potential direct-current voltage lead-out of the rectifier and the junction point where the filter is joined to the heated circuit, Fig. 10 shows a device, wherein the rectifier is in-stalled on a separate supply substation far from the transmit-ting substation coupled to the ice melting line and is coupledto the melting circuit via connecting lines;
Fig. ll shows a device, wherein the rectifier and the filter are mounted on a separate supply substation, i Fig. 12 shows a device comprising a filter and an adjust-able voltage source coupled in series thereto;
Fig. 13 shows possible embodiments featuring different ways of connecting the adjustable voltage source in series into the current filter circuit;
Fig. 14 shows an embodiment of an automatically adjust-able commercial frequency voltage source.
_ g _ 1~83Z31 Referring to Fig. 1, an overhead ice melting lineconductor 1 is disconnected from busbars 2 and 3 of the transmitting and receiving substations and is connected from one end directly to a grounding device 4 and from the other end to a grounding device 5 via a rectifier 6. A
current filter comprising a capacitor bank 7 and a reactor 8 is placed in parallel with the direct-current voltage lead-out wires of the rectifier. The busbars 2 and 3 of the transmitting and receiving substations are also connected to -10 the operating conductors 9 and 10 and transformers (auto-transformers) 11 and 12 provided with neutral wires coupled to the grounding devices 5 and 4, respectively.
Fig. 1 shows the embodiment wherein the filter compris-es the capacitor bank 7 and the reactor 8 connected in se-ries and tuned in resonance on the commercial frequency. The reactor can, generally, be made up of several series-connected and parallel-connected reactors. In case the vari-able current component is present in the melting circuit, only the voltage drop of the variable current component of . .
-~20 the filter circuit is applied to the valves and the insula-tion of the rectifier 6. As the filter is tuned on the commercial frequency in resonance, the voltage drop thereon is close to zero and is determined in the steady-state ~-operation by the effective resistance of the filter only.
,: .
, ~-i '' 1 - 10 - ~,, ','' ` ' ~ .
,#
.. ,, .. .. .. . , - . .. ` . ~........ . . ,. .. ` . . , The bulk of -the commercial frequency current flows through the filter bypassing the rectifier 6. The capacitor bank 7 is to be selected with regard to the direct-voltage component equal to the rectified voltage of the rectifier 6.
Direct current i5 closed through the circuit "pole of the rectifier 6 - conductor 1 of the line - ground -another pole of the rectifier 6.
When short-circuit current flows in the conductors 9 and 10, the voltage on the filter elements increases in proportion with the increase of the induced current in the conductor 1. m e lead-out wires of the rectifier 6 receive only the voltage drop on the equivalent resistance of the - filter conditioned by inaccuracy of tuning of its elements and the presence of the reactor effective resistance.
When short circuit currents appear in the operating conductors 9 and 10 of the line, the induced currents-in i the conductor 1 exceed the induced currents in the normal - conditions. Voltages and currents, which the capacitor 7 and the reactor 8 should withstand, increase sufficiently.
In order to reduce the installed capacity of the filter ele-ments a discharger 13 (Fig. 2) is set up parallel to one of these elements. It i9 convenient to set up the discharger 13 parallel to the reactor 8 of the filter, because, when the discharger 13 shunts the capacitor bank 7, a direct current short circuit occurs. When the discharger 13 operates, the total resistance of the filter sharply /
.
., ... . . ,, , . . . . ~
~083Z3~
rises and alternating current is mainly closed throuyh the rectifier 6.
As such a condition is very brief, the result:ing magnetization of the transformer (not shown in Fig. 2) supplying the rectifier 6 is not dangerous. Owing to the short distance between the electrodes of the discharger 13, the arc produced when the discharger 13 operates may not cease, which may require in some cases disconnection of the operating conductors 9 and 10 of the line, though the short circuit is eliminated.
Operation of the discharger 13 with the disconnected supply of the rectifier 6 is the most dangerous case in these conditions. There is no way for the induced current to flow to and the c,urrent through the discharger 13 in such conditions reaches its maximum.
In such situations it is advantageous to use the device of Fig. 3. Here a switchgear device is connected parallel to the current filter to shunt it and in order to do quick switchings in the rectifier supply circuit and thus to increase the reliability of operation of the filter and the dischargers. The command to turn on the switchgear device 14 is fed from the sensors (not shown in Fig. 3 ) responding to operation of the discharger 13.
Referring to Fig. 4, the current filter is made up ' of the capacitor bank 7 and the reactor 8 connected in series with said capacitor bank 7 via a matching transformer 15.
.~ '' .
. .
1083;23:1 Direct current is shorted through the circuit: a pole of the rectifier 6 - conductor 1 of the line - ground -another pole of the rectifier 6. Alternating current induced in the conductor 1 by the currents of the conductors 9 and 10 is generally shorted in the normal operating conditions through the current filter. me filter currents which do not exceed nominal values should not cause saturation of the magnetic circuit of the transformer 15. When induced current exceeds the nominal value, which may occur during a short circuit, the magnetization current of the transformer . 15 rises sharply owing to saturation of the magnetic circuit.
In this case the summated induction of the reactor 8 and the transformer 15 drops, which results in mismatching of the filter elements. The total resistance of the filter grows.
The paths of shortening induced currents change.
In emergency conditions induced currents flow mainly . . ~
through the circuit: conductor 1 - rectifier 6 - winding of ~ . .
the supply transformer (not shown in Fig. 4) - rectifier 6 -~; ground. Due to the transient nature of the emergency condition magnetization of the transformer, supplying the rectifier, is not dangerous.
:
Referring to Figs. S to 7, an impedance 16 is included between the lead-out wires of the current filter and lead-, outs of the rectifier 6 into the direct current circuit of ~; the rectifier 6 in order to increase the impedance to .. :
~ , :' I ~ , . ; .
., . ~ , - 13 -,, .
, .. . .
~:
alternating current. Since the rectifier 6 and the current filter are placed in parallel, the increase of impedance in a branch of the rectifier leads to reduction of the alternating induced current therein and, consequently, to better filtration of said current.
The device of Fig. 5 comprises said impedance 16 con-nected between the ground and the direct-current voltage lead-out of the rectifier 6. Such design of the device is more advantageous when cables of the overhead power trans-mission lines are used as the impedance 16. The insulation of the cables is not thick, but is quite sufficient to -~withstand the voltage drop of the melting current on the cable impedance. It should be noted that the cables can be grounded by connection to grounding devices along the line or at another substation. Connection of cables in accordance with the above described circuit may have the object of heat- -~
ing these cables or melting the ice thereupon.
The device of Fig. 6 features a current-limiting imped-ance 16 connected from the side of the linear (potential) lead-out of the rectifier 6 between said lead-out and the current filter. Conductors of the power transmission linbs can be effectively used as said impedance, because their insulation is good enough for the purpose. These may be conductors of some line connecting the transmitting sub-station, whereto the line to be heated for ice melting with ~`
the conductors 1, 9, 10 leads and where the current filter is .
.
- D 14~
~ r - .
` ` . ` , ` . ~ -- ~
installed, with the supply substation, where the rectifier 6 is installedO Conductors of such connecting line may serve as the current-limiting impedance and as a means for join-ing the rectifier 6 when it is located far from the ice melting line with the conductors 1, 9, 10. Besides, prevent-ive heating or ice melting can be performed simultaneously on the conductors of the connecting line. In the other case, when the rectifier 6, the current filter and the line com-prising conductors 1, 9, 10 whereon the icing is to be melted are situated at one substation, the impedance 16 may be some other line having lead-outs at said substation, which can be connected between the potential lead-out of the rectifier 6 and the current filter.
In some cases, when there is no one impedance available sufficient for the purpose or due to some other reasons, two current-limiting impedances can be connected. In this case one of them is connected to the rectifier 6 (Fig. 7) from the side of the potential lead-out, that is from the heated conductor 1, and the other to the grounding device 5.
When the ice is melted on conductors of the overhead .~
power transmission line leading from the same substation where the rectifier 6 is installed and conductors or cables of other lines are impossible or inadvisable to use, it is ` advantageous to employ reactors 17 as impedances, as shown in ~igs. 8 and 9.
~ - ' ~' i,, " 13 '; ~ ' ' '' ' `: '' '' The use of the reactors 17 in the direct current circuit leaves the direct current melting condition unaffected but significantly influences current redistribution between parallel branches of the current filter and the rectifier 6. Connection of the reactor 17 between the lead-out of the rectifier 6 and the ground (Fig. 8) permits minimum in-sulation of the reactor 17, as well as limitation of over-currents through the valves of the rectifier 6 during short circuits through the ground to the supply rectifier 6 of the alternating current circuit (not shown in Fig. 8). Connect-ion of the reactor 17 between the potential lead-out of the rectifier 6 and the connecting point of the current filter and the heated circuit (Fig. 9) can be useful, for example, due to conditions of the high-frequency link via the heated conductor of the overhead power transmission line.
The embodiment of the device of Fig. 10 is a typical example of the use of conductors and cables of power trans-mission lines as current-limiting impedances. There can be , . .
no rectifier at the transmitting substation whose busbars 2 are coupled to the power transmission line with the conduct-ors 1, 9, 10 whereon the icing is to be melted. In this case a rectifier 6 installed at another substation can be used for ice melting~ If there exist power transmission lines conneci-ing the supply and transmission substations on some voltage, their conductors and aables can be used both as conductors for .
i,.:
~ - 16 -- '.' . ~ ~ : ' ;
coupling the far-away rectifier 6 to the heated line and as current-limiting resistances in order to reduce the variable current component in the rectifier branch. It is evident that for such purposes those lines should be used, whose conductors or cables require preventive heating or ice melting and possess acceptable electrical parameters.
Referring to Fig. 10, conductors 18 of the coupling line are connected between the potential lead-out of the rectifier 6 and the point where the current filter (capacitor 7) is joined to the conductor 1. A conductor or conductors of one phase can be used as the conductors 18, as well as conductors of several phases of the coupling line, which are connected in series or parallel to one another. The functions of the serond impedance connected between the other lead-out of the rectifier 6 and the grounding device 5 can be performed by cables 19 of the coupling line or parallel-connected cables of several lines. The cables can be grounded by connecting to the grounding device 5 of the transmitting substation or by connecting to other grounding devices available on the line or at other substations. In this case the rectifier 6 and the current filter are situated at different substations.
When it is necessary to install the current filter and the rectifier 6 at one supplying substation and perform phase-by-phase ice melting on the overhead line leading from the busbars of another, that is intermediate, substation, ;
. ... . .. . ~ . . .,.~. -1083;~31 the conductors 18 and the cables 19 of the coupling line can be employed simultaneously for supplying direct-current voltage to the heated circuit (for example, two phases of the coupling line) and for distribution of induced current between parallel-connected branches of the rectifier 6 and the current filter (one phase 18 of the coupling line and its cables 1~) as shown in Fig. 11.
The summated uncompensated filter impedance may be the reason of a considerable leak of alternating current into the rectifier branch. In order to compensate the internal impedance of the filter, it is proposed to connect in series into its circuit a voltage source 20 tFig. 12).
The value and phase of the voltage of the source 20 is con- !
ditioned by the load conditions, line parameters and the phase of the induced current. If the phase and magnitude of the voltage of the source 20 are selected correctly, all the induced current is directed to the filter and this is bene-ficient for the operating conditions of the transformer supplying the rectifier 6.
Referring to Fig. 13, the device comprises a reactor 8 of the filter which is connected in series with the capacitor 7 via the matching transformer 15. In this case the adjust-able voltage source 20 can be connected in two ways. It can be connected in series into the circuit: capacitor 7 -primary winding of the transformer 15 (shown by dotted line in Fig. 13), or the source 20 can be connected together ~ 1 !
.;-' ' ' '''' 1~
~ .
.
with the reactor 8 into the circuit of the secondary wi.nd-ing of the transformer 15.
Fig. 14 shows a concrete example of automatic ad-justing of the magnitude of the phase of the voltage source.
It becomes pos~ible due to the rigid tie between the current magnitude and phase in the neutral wire of the transformer (autotransformer) 11 coupled to the operating phases of the heated line and the induced current in the disconnected conductor 1 of the overhead line. A single-phase transformer 21 is used as the voltage source. The secondary winding of the transformer 21 is connected in series with a filter 22.
The primary winding is connected in tandem with the circuit of the grounded neutral wire of said transformer 11, whereas a switchgear device 23 is connected parallel..thereto, said device 23 being turned on in the absence of melting. After the circuit is made up and direct-current voltage is supplied to the rectifier 6, the switchgear device 23 is cut off and the induced current is forcibly shorted through the filter 22. The ratio of transformation of the ~ingle-phase trans-former 21 is equal to the ratio of the current in the neutral wire of the transformer 11 to the induced current in the : ~:
conductor 1.
It is important to point out that the requiredpower of the voltage source connected in series with the filter is not as a rule over 10-15 kwt. In this case the installed t , ' ,' ~ , ' ' ~ ' , ' ~
108323~
power of the filter elements can be reduced manyfold.
Since there exists a phase shift between currents in the conductor 1 and the neutral wire of the transformer 11 owing to the effect of the effective resistance of the conductor 1, it is advisable to connect a complex load 2-4 parallel to the secondary winding of the transformer 21 in order to reduce the current flow to the circuit of the rectifier 6. ~he nature of the load 24 is conditioned by the r nature of the unbalance of the elements of a concrete filter. In each case parameters of the load 24 are defined by means of calculations.
' .
. - 20 -: f . ,. . . ~, . . .. ..
: : ~
.
~083Z31 to the ice melting circuit due to electromagnetic and electrostatic interferences of the two operating phases.
As a result current in the ice melting circuit comprises two distinct components: a permanent component caused by the rectifier EMF and an alternating component of the commercial (power-circuit) frequency caused by the induc-ed EMF.
The EMF and the variable component of the rectified current induced in the melting circuit of lines using up to 3S kv, inclusive, are not dangerous for 10 kv rectifiers employed for ice melting. For 110 kv lines and upwards these induced currents and voltages are dangerous and inadmissib-le for such rectifiers and their supply transformers. It becomes impossible to use 10-35 kv rectifier bridges and, sometimes, to melt the ice by means of phase by phase dis-connection of 110 kv lines and upwards.
Besides, in such devices overvoltages tend to appear on valves and insulation of the rectifier, when it is put in and out of operation.
When the ice melting circuit is connected (the recti-fier is put into operation), the induced alternating electro~
motive force whose polarity is the opposite of the valve conduction is applied to the lead-outs of the non-conduct-ing rectifier. The open circuit voltage reaches several tens of thousands volts, which can be dangerous both for the valves and for the insulation of the rectifier. The ;
_ 3 -::~A.
~, ..
., ", . .
1~)83Z31 other half-wave of the induced electromotive force coinci-des with the valve conduction direction and causes current pulsations in the ice melting circuit. In this case it is only the voltage drop on valves and connecting wires of the rectifier that is applied to the valves and insulation of the rectifier.
When the rectifier is put out of operation and its supply of alternating current is cut off, the rectified current drops to zero. All the induced electromotive force in the line conductor is then also applied to the valves and insulation of the rectifier, when its polarity is opposite to the valve conduction. This electromotive force is not dangerous for the installation in the other half-period.
As a result, large induced electromotive force, especi-ally when short circuit currents flow through the operating ~ . :
conductors of the line, requires that the number of series-connected valves in the rectifier arms be increased and its insulation be strengthened, that is the rectifier is to be made more powerful.
.~
When some phase is inoperative in the line during -ice melting, the alternating electromotive force induced in the disconnected conductor is the cause of the melting current variable component. In this case the rectified current of the rectifier is pulsing and the pulsation fre-quency is equal to the power-circuit frequency. Such pulsa-~' :'~
?
'. ;l ~A~
... . . . . .. . .
tions of the rectifier current result in direct components of the rectifier phase currents and, consequently, in the windings of the transformer supplying the rectifier. Direct current components lead to appearance of constant uncom-pensated magnetization fluxes, increase of the magnetization current and losses of power and energy in the steel of the rectifier supplying transformer.
Such magnetization becomes dangerous when the amplitude of the variable component in the rectified current does exceed the relative nominal transformer current by 5 or more percent but is within the limits of 5 or more percent rela-tive to nominal transformer current. The transformer cannot be allowed to operate under suàh conditions.
It is an object of this invention to eliminate the above listed drawbacks.
; Another object of this invention is to cut down over-voltages on the valves and insulation of the rectifier, which are produced when it is put in and out of operation.
~;! Yet another object of the invention is to prevent the ~-/ 20 alternating current of the ice melting circuit flowing through the rectifier.
This is achieved by that a commercial (power-line~
frequency current filter connected in parallel to the direct-current voltage lead-out wires of the rectifier.
The current filter is advisable to be made of at least one capacitor and at least one reactor connected in series.
., ,.
,, .
~ - 5 -;~; .
,:~
.
~ ~, `': iqA-108~ 31 Besides, in order to reduce the installed powers and, consequently, the price of the filter elements, it is advantageous to connect a discharger, e.g. a spark discharger, parallel to one of the filter elements, and in order to increase the reliability of operation to connect a switchgear device parallel to the filter, said device being turned on at the moment when said discharger operates.
The above listed objects are also achieved by connect-ing the filter reactor in series with the capacitor via the matching transformer.
It is also advantageous to connect at least one impedance~
between the lead-out wires of the current filter and the direct current lead-out of the rectifier.
The impedance can be connected either between the potential ungrounded lead-out of the rectifier and the junction point where the filter is joined to the line, or between the ; lead-out wire of the rectifier and the ground, or, when two impedances are used, one impedance can be connected between the potential lead-out of the rectifier and the current filter, 20 whereas the other impedance between the other lead-out of the rectifier and the second lead-out wire of the filter.
Reactors, conductors, cables of other overhead lines leading from the busbars of the substation where the rectifier is installed, or reactors of the current filter can be used as !
a current-limiting impedance.
., ' These objects are also achieved by connecting a commer-cial frequency voltage source whose phase and voltage can be regulated, in series into the circuit of the filter.
The most advantageous device which can be used as said voltage source is a single-phase transformer whose primary winding is connected in tandem with the neutral lead-out of the high-voltage winding of the transformer (autotrans-former) coupled to two operating phases of the heated line.
In order to more accurately compensate the alternating induced current in the direct current circuit of the rectifier it is advantageous to connect a matching complex load parallel to the secondary winding of said single-phase transformer, the parameters of said load being determined by the nature of the unbalance of the commercial frequency filter elements.
The disclosed device permits ice melting by means of phase-by-phase disconnection of conductors of the 110 kv line and upwards using industrially produced power rectifying ~; bridges of the 10 kv and 35 kv classes.
~; 20 The filter is installed parallel to the rectifier from the direct current side and this ensures a by-pass for the melting current variable component in the conductor.
As a result the rectifier current becomes more ideally smoothed and there are no direct components in the rectifier phase currents, whereas magnetization of the supply (anode) transformer is completely eliminated.
,. ~
~;
~.,, (~
. .
~,A; , Besides, the alternatiny induced electromotive force results in producing current in the circuit: disconnected conductor - current filter - ground - disconnected conductor.
Since the filter is tuned in resonance on the power-line frequency, the voltage drop thereupon caused by the current produced by the induced electromotive force is insignificant (equal to zero in an ideal case) and, consequently, over-voltages produced in the rectifier, when it is put into and out of operation, are eliminated.
In accordance with a specific embodiment, a device for melting icing by direct current through the conductors of an overhead power transmission line featuring transformers with grounded neutral wires connected thereto, comprises: a rectifier connected for the ice melting period by its direct-current voltage lead-out wires to at least one disconnected conductor of the power transmission line and a grounding circuit: and a commercial frequency circuit filter connected parallel to the direct-current voltage lead-outs of said rectifier.
The invention will now be described with reference to a specific embodiment thereof, taken in conjunction with the accompanying drawings, wherein:
Fig. 1 shows a schematic circuit diagram of an ice melting device featuring a commercial frequency filter coupled parallel to the direct-current voltage lead-outs of the rectifier:
Fig. 2 shows a similar device of Figure 1 and featuring a filter, whose one element is shunted by a discharger:
Fig. 3 shows a device of Figure 2, featuring an addition-al switchgear installation placed in parallel with the filter:
. .
.
~, - . : . . .- - -. .: . -. . .
108323~
Fig. 4 shows a device featuring a filter whose reactor is coupled via a matching transformer, Fig. 5 shows a device, wherein an impedance is connected between the ground and the direct-current voltage lead-out of the rectifier, Fig. 6 shows a device, wherein an impedance is connected between the potential direct-current voltage lead-out of the rectifier and the junction point where the filter is joined to the heated circuit, Fig. 7 shows a device featuring two current-limiting impedances connected in series with the rectifier from the side of the line and from the side of the ground.
Figs. 8 and 9 show devices, wherein impedances are reactors connected respectively between the ground and a pole of the rectifier, as well as between the potential direct-current voltage lead-out of the rectifier and the junction point where the filter is joined to the heated circuit, Fig. 10 shows a device, wherein the rectifier is in-stalled on a separate supply substation far from the transmit-ting substation coupled to the ice melting line and is coupledto the melting circuit via connecting lines;
Fig. ll shows a device, wherein the rectifier and the filter are mounted on a separate supply substation, i Fig. 12 shows a device comprising a filter and an adjust-able voltage source coupled in series thereto;
Fig. 13 shows possible embodiments featuring different ways of connecting the adjustable voltage source in series into the current filter circuit;
Fig. 14 shows an embodiment of an automatically adjust-able commercial frequency voltage source.
_ g _ 1~83Z31 Referring to Fig. 1, an overhead ice melting lineconductor 1 is disconnected from busbars 2 and 3 of the transmitting and receiving substations and is connected from one end directly to a grounding device 4 and from the other end to a grounding device 5 via a rectifier 6. A
current filter comprising a capacitor bank 7 and a reactor 8 is placed in parallel with the direct-current voltage lead-out wires of the rectifier. The busbars 2 and 3 of the transmitting and receiving substations are also connected to -10 the operating conductors 9 and 10 and transformers (auto-transformers) 11 and 12 provided with neutral wires coupled to the grounding devices 5 and 4, respectively.
Fig. 1 shows the embodiment wherein the filter compris-es the capacitor bank 7 and the reactor 8 connected in se-ries and tuned in resonance on the commercial frequency. The reactor can, generally, be made up of several series-connected and parallel-connected reactors. In case the vari-able current component is present in the melting circuit, only the voltage drop of the variable current component of . .
-~20 the filter circuit is applied to the valves and the insula-tion of the rectifier 6. As the filter is tuned on the commercial frequency in resonance, the voltage drop thereon is close to zero and is determined in the steady-state ~-operation by the effective resistance of the filter only.
,: .
, ~-i '' 1 - 10 - ~,, ','' ` ' ~ .
,#
.. ,, .. .. .. . , - . .. ` . ~........ . . ,. .. ` . . , The bulk of -the commercial frequency current flows through the filter bypassing the rectifier 6. The capacitor bank 7 is to be selected with regard to the direct-voltage component equal to the rectified voltage of the rectifier 6.
Direct current i5 closed through the circuit "pole of the rectifier 6 - conductor 1 of the line - ground -another pole of the rectifier 6.
When short-circuit current flows in the conductors 9 and 10, the voltage on the filter elements increases in proportion with the increase of the induced current in the conductor 1. m e lead-out wires of the rectifier 6 receive only the voltage drop on the equivalent resistance of the - filter conditioned by inaccuracy of tuning of its elements and the presence of the reactor effective resistance.
When short circuit currents appear in the operating conductors 9 and 10 of the line, the induced currents-in i the conductor 1 exceed the induced currents in the normal - conditions. Voltages and currents, which the capacitor 7 and the reactor 8 should withstand, increase sufficiently.
In order to reduce the installed capacity of the filter ele-ments a discharger 13 (Fig. 2) is set up parallel to one of these elements. It i9 convenient to set up the discharger 13 parallel to the reactor 8 of the filter, because, when the discharger 13 shunts the capacitor bank 7, a direct current short circuit occurs. When the discharger 13 operates, the total resistance of the filter sharply /
.
., ... . . ,, , . . . . ~
~083Z3~
rises and alternating current is mainly closed throuyh the rectifier 6.
As such a condition is very brief, the result:ing magnetization of the transformer (not shown in Fig. 2) supplying the rectifier 6 is not dangerous. Owing to the short distance between the electrodes of the discharger 13, the arc produced when the discharger 13 operates may not cease, which may require in some cases disconnection of the operating conductors 9 and 10 of the line, though the short circuit is eliminated.
Operation of the discharger 13 with the disconnected supply of the rectifier 6 is the most dangerous case in these conditions. There is no way for the induced current to flow to and the c,urrent through the discharger 13 in such conditions reaches its maximum.
In such situations it is advantageous to use the device of Fig. 3. Here a switchgear device is connected parallel to the current filter to shunt it and in order to do quick switchings in the rectifier supply circuit and thus to increase the reliability of operation of the filter and the dischargers. The command to turn on the switchgear device 14 is fed from the sensors (not shown in Fig. 3 ) responding to operation of the discharger 13.
Referring to Fig. 4, the current filter is made up ' of the capacitor bank 7 and the reactor 8 connected in series with said capacitor bank 7 via a matching transformer 15.
.~ '' .
. .
1083;23:1 Direct current is shorted through the circuit: a pole of the rectifier 6 - conductor 1 of the line - ground -another pole of the rectifier 6. Alternating current induced in the conductor 1 by the currents of the conductors 9 and 10 is generally shorted in the normal operating conditions through the current filter. me filter currents which do not exceed nominal values should not cause saturation of the magnetic circuit of the transformer 15. When induced current exceeds the nominal value, which may occur during a short circuit, the magnetization current of the transformer . 15 rises sharply owing to saturation of the magnetic circuit.
In this case the summated induction of the reactor 8 and the transformer 15 drops, which results in mismatching of the filter elements. The total resistance of the filter grows.
The paths of shortening induced currents change.
In emergency conditions induced currents flow mainly . . ~
through the circuit: conductor 1 - rectifier 6 - winding of ~ . .
the supply transformer (not shown in Fig. 4) - rectifier 6 -~; ground. Due to the transient nature of the emergency condition magnetization of the transformer, supplying the rectifier, is not dangerous.
:
Referring to Figs. S to 7, an impedance 16 is included between the lead-out wires of the current filter and lead-, outs of the rectifier 6 into the direct current circuit of ~; the rectifier 6 in order to increase the impedance to .. :
~ , :' I ~ , . ; .
., . ~ , - 13 -,, .
, .. . .
~:
alternating current. Since the rectifier 6 and the current filter are placed in parallel, the increase of impedance in a branch of the rectifier leads to reduction of the alternating induced current therein and, consequently, to better filtration of said current.
The device of Fig. 5 comprises said impedance 16 con-nected between the ground and the direct-current voltage lead-out of the rectifier 6. Such design of the device is more advantageous when cables of the overhead power trans-mission lines are used as the impedance 16. The insulation of the cables is not thick, but is quite sufficient to -~withstand the voltage drop of the melting current on the cable impedance. It should be noted that the cables can be grounded by connection to grounding devices along the line or at another substation. Connection of cables in accordance with the above described circuit may have the object of heat- -~
ing these cables or melting the ice thereupon.
The device of Fig. 6 features a current-limiting imped-ance 16 connected from the side of the linear (potential) lead-out of the rectifier 6 between said lead-out and the current filter. Conductors of the power transmission linbs can be effectively used as said impedance, because their insulation is good enough for the purpose. These may be conductors of some line connecting the transmitting sub-station, whereto the line to be heated for ice melting with ~`
the conductors 1, 9, 10 leads and where the current filter is .
.
- D 14~
~ r - .
` ` . ` , ` . ~ -- ~
installed, with the supply substation, where the rectifier 6 is installedO Conductors of such connecting line may serve as the current-limiting impedance and as a means for join-ing the rectifier 6 when it is located far from the ice melting line with the conductors 1, 9, 10. Besides, prevent-ive heating or ice melting can be performed simultaneously on the conductors of the connecting line. In the other case, when the rectifier 6, the current filter and the line com-prising conductors 1, 9, 10 whereon the icing is to be melted are situated at one substation, the impedance 16 may be some other line having lead-outs at said substation, which can be connected between the potential lead-out of the rectifier 6 and the current filter.
In some cases, when there is no one impedance available sufficient for the purpose or due to some other reasons, two current-limiting impedances can be connected. In this case one of them is connected to the rectifier 6 (Fig. 7) from the side of the potential lead-out, that is from the heated conductor 1, and the other to the grounding device 5.
When the ice is melted on conductors of the overhead .~
power transmission line leading from the same substation where the rectifier 6 is installed and conductors or cables of other lines are impossible or inadvisable to use, it is ` advantageous to employ reactors 17 as impedances, as shown in ~igs. 8 and 9.
~ - ' ~' i,, " 13 '; ~ ' ' '' ' `: '' '' The use of the reactors 17 in the direct current circuit leaves the direct current melting condition unaffected but significantly influences current redistribution between parallel branches of the current filter and the rectifier 6. Connection of the reactor 17 between the lead-out of the rectifier 6 and the ground (Fig. 8) permits minimum in-sulation of the reactor 17, as well as limitation of over-currents through the valves of the rectifier 6 during short circuits through the ground to the supply rectifier 6 of the alternating current circuit (not shown in Fig. 8). Connect-ion of the reactor 17 between the potential lead-out of the rectifier 6 and the connecting point of the current filter and the heated circuit (Fig. 9) can be useful, for example, due to conditions of the high-frequency link via the heated conductor of the overhead power transmission line.
The embodiment of the device of Fig. 10 is a typical example of the use of conductors and cables of power trans-mission lines as current-limiting impedances. There can be , . .
no rectifier at the transmitting substation whose busbars 2 are coupled to the power transmission line with the conduct-ors 1, 9, 10 whereon the icing is to be melted. In this case a rectifier 6 installed at another substation can be used for ice melting~ If there exist power transmission lines conneci-ing the supply and transmission substations on some voltage, their conductors and aables can be used both as conductors for .
i,.:
~ - 16 -- '.' . ~ ~ : ' ;
coupling the far-away rectifier 6 to the heated line and as current-limiting resistances in order to reduce the variable current component in the rectifier branch. It is evident that for such purposes those lines should be used, whose conductors or cables require preventive heating or ice melting and possess acceptable electrical parameters.
Referring to Fig. 10, conductors 18 of the coupling line are connected between the potential lead-out of the rectifier 6 and the point where the current filter (capacitor 7) is joined to the conductor 1. A conductor or conductors of one phase can be used as the conductors 18, as well as conductors of several phases of the coupling line, which are connected in series or parallel to one another. The functions of the serond impedance connected between the other lead-out of the rectifier 6 and the grounding device 5 can be performed by cables 19 of the coupling line or parallel-connected cables of several lines. The cables can be grounded by connecting to the grounding device 5 of the transmitting substation or by connecting to other grounding devices available on the line or at other substations. In this case the rectifier 6 and the current filter are situated at different substations.
When it is necessary to install the current filter and the rectifier 6 at one supplying substation and perform phase-by-phase ice melting on the overhead line leading from the busbars of another, that is intermediate, substation, ;
. ... . .. . ~ . . .,.~. -1083;~31 the conductors 18 and the cables 19 of the coupling line can be employed simultaneously for supplying direct-current voltage to the heated circuit (for example, two phases of the coupling line) and for distribution of induced current between parallel-connected branches of the rectifier 6 and the current filter (one phase 18 of the coupling line and its cables 1~) as shown in Fig. 11.
The summated uncompensated filter impedance may be the reason of a considerable leak of alternating current into the rectifier branch. In order to compensate the internal impedance of the filter, it is proposed to connect in series into its circuit a voltage source 20 tFig. 12).
The value and phase of the voltage of the source 20 is con- !
ditioned by the load conditions, line parameters and the phase of the induced current. If the phase and magnitude of the voltage of the source 20 are selected correctly, all the induced current is directed to the filter and this is bene-ficient for the operating conditions of the transformer supplying the rectifier 6.
Referring to Fig. 13, the device comprises a reactor 8 of the filter which is connected in series with the capacitor 7 via the matching transformer 15. In this case the adjust-able voltage source 20 can be connected in two ways. It can be connected in series into the circuit: capacitor 7 -primary winding of the transformer 15 (shown by dotted line in Fig. 13), or the source 20 can be connected together ~ 1 !
.;-' ' ' '''' 1~
~ .
.
with the reactor 8 into the circuit of the secondary wi.nd-ing of the transformer 15.
Fig. 14 shows a concrete example of automatic ad-justing of the magnitude of the phase of the voltage source.
It becomes pos~ible due to the rigid tie between the current magnitude and phase in the neutral wire of the transformer (autotransformer) 11 coupled to the operating phases of the heated line and the induced current in the disconnected conductor 1 of the overhead line. A single-phase transformer 21 is used as the voltage source. The secondary winding of the transformer 21 is connected in series with a filter 22.
The primary winding is connected in tandem with the circuit of the grounded neutral wire of said transformer 11, whereas a switchgear device 23 is connected parallel..thereto, said device 23 being turned on in the absence of melting. After the circuit is made up and direct-current voltage is supplied to the rectifier 6, the switchgear device 23 is cut off and the induced current is forcibly shorted through the filter 22. The ratio of transformation of the ~ingle-phase trans-former 21 is equal to the ratio of the current in the neutral wire of the transformer 11 to the induced current in the : ~:
conductor 1.
It is important to point out that the requiredpower of the voltage source connected in series with the filter is not as a rule over 10-15 kwt. In this case the installed t , ' ,' ~ , ' ' ~ ' , ' ~
108323~
power of the filter elements can be reduced manyfold.
Since there exists a phase shift between currents in the conductor 1 and the neutral wire of the transformer 11 owing to the effect of the effective resistance of the conductor 1, it is advisable to connect a complex load 2-4 parallel to the secondary winding of the transformer 21 in order to reduce the current flow to the circuit of the rectifier 6. ~he nature of the load 24 is conditioned by the r nature of the unbalance of the elements of a concrete filter. In each case parameters of the load 24 are defined by means of calculations.
' .
. - 20 -: f . ,. . . ~, . . .. ..
Claims (16)
1. A device for melting icing by direct current through the conductors of an overhead power transmission line featuring transformers with grounded neutral wires connected thereto, comprising: a rectifier connected for the ice melting period by its direct-current voltage lead-out wires to at least one disconnected conductor of the power transmission line and a grounding circuit; and a commercial frequency circuit filter connected parallel to the direct-current voltage lead-outs of said rectifier.
2. A device as claimed in claim 1, wherein said commer-cial frequency current filter is made up of at least one reactor and at least one capacitor connected in series.
3. A device as claimed in claim 2, wherein said current filter includes a discharger coupled parallel to either said reactor or said capacitor.
4. A device as claimed in claim 3, wherein said current filter includes a switchgear device connected parallel thereto and turned on when current appears in the circuit of said discharger.
5. A device as claimed in claim 2, wherein the current filter includes a transformer whose primary winding is connected in series with said at least one capacitor and said at least one reactor is connected into the circuit of the secondary winding.
6. A device as claimed in claim 1, wherein at least one impedance is connected between the lead-outs of said current filter and the direct-current voltage lead-outs of said rectifier.
7. A device as claimed in claim 1, wherein an impedance is connected between the potential lead-out of said rectifier and the point where said filter is coupled to the power transmission line.
8. A device as claimed in claim 6, wherein said impedance is connected between the lead-out of said rectifier and the grounding circuit.
9. A device as claimed in claim 6, comprising two impedances of which one is connected between the potential lead-out of said rectifier and said current filter and the other impedance is connected between the other lead-outs of the rectifier and the grounding circuit.
10. A device as claimed in claim 6, wherein reactors are used as impedances.
11. A device as claimed in claim 6, wherein conductors and cables of other overhead power transmission lines are used as impedances.
12. A device as claimed in claim 11, wherein said rectifier is installed at a supply substation far from the substation to which said power transmission line is connected for the ice melting, conductors, as well as cables of lines joining said substations, being used as said impedances.
13. A device as claimed in claim 11, wherein said rectifier and said current filter are installed at a supply substation far from the substation to which said power trans-mission line is connected for the ice melting, one of the conductors joining the substations of the line being used as said impedance and as conductors feeding direct current to the ice melting line, one end being grounded on the side of the substation to which said power transmission line is joined and the second end being coupled to a pole of the rectifier, the potential lead-out of said rectifier being connected to the ice melting line via other conductors of the coupling line.
14. A device as claimed in claim 1, wherein said current filter includes a source of commercial frequency voltage which can be adjusted as to phase and magnitude connected in series into the circuit of said filter.
15. A device as claimed in claim 14, wherein a second winding of a single-phase transformer serves as the source whose commercial frequency voltage can be adjusted in phase and magnitude, the primary winding thereof being connected to the neutral wire of the high-voltage winding of said transformer coupled to two phases of the heated overhead power transmission line and to the grounding circuit.
16. A device as claimed in claim 15, wherein a matching complex load is connected parallel to said secondary winding of the single-phase transformer, which is coupled in series to the circuit of the commercial frequency current filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA279,534A CA1083231A (en) | 1977-05-31 | 1977-05-31 | Device for melting the icing by direct current on conductors of overhead power transmission line |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA279,534A CA1083231A (en) | 1977-05-31 | 1977-05-31 | Device for melting the icing by direct current on conductors of overhead power transmission line |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1083231A true CA1083231A (en) | 1980-08-05 |
Family
ID=4108776
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA279,534A Expired CA1083231A (en) | 1977-05-31 | 1977-05-31 | Device for melting the icing by direct current on conductors of overhead power transmission line |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1083231A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109033690A (en) * | 2018-08-16 | 2018-12-18 | 四川大学 | Heating transmission pressure even power optimization method certainly based on exchange heating power supply |
| CN113937705A (en) * | 2021-10-15 | 2022-01-14 | 中铁第一勘察设计院集团有限公司 | Alternating-current ice melting device for railway traction network and control method thereof |
-
1977
- 1977-05-31 CA CA279,534A patent/CA1083231A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109033690A (en) * | 2018-08-16 | 2018-12-18 | 四川大学 | Heating transmission pressure even power optimization method certainly based on exchange heating power supply |
| CN109033690B (en) * | 2018-08-16 | 2022-10-11 | 四川大学 | Self-heating transmission conductor uniform power optimization method based on alternating-current heating power supply |
| CN113937705A (en) * | 2021-10-15 | 2022-01-14 | 中铁第一勘察设计院集团有限公司 | Alternating-current ice melting device for railway traction network and control method thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4082962A (en) | Device for melting the icing by direct current on conductors of overhead power transmission line | |
| US4085338A (en) | High-voltage network for areas with high rate of icing | |
| CA1138984A (en) | Rate sensing instantaneous trip mode network | |
| EP0172254B1 (en) | High frequency noise absorbing circuit | |
| US4119866A (en) | High voltage electrical network with DC ice-melting device and current return through ground | |
| CA2541323A1 (en) | Distributed floating series active impedances for power transmission systems | |
| EP1766746A1 (en) | Method and equipment for the protection of power systems against geomagnetically induced currents | |
| WO2021227267A1 (en) | On-line ice-melting apparatus | |
| WO2021227268A1 (en) | On-line ice-melting apparatus | |
| US6650523B1 (en) | Protective device, in particular a fault current protective device | |
| CN106856323B (en) | Protection device for protecting transformer from influence of geomagnetic induction current | |
| AU2535688A (en) | Phase loss detection circuit including transient protection | |
| CA1083231A (en) | Device for melting the icing by direct current on conductors of overhead power transmission line | |
| Kletsel et al. | Construction of resource-saving differential protections for converter units with transformers with 2N secondary windings and 2N rectifiers | |
| Asghar | Elimination of inrush current of transformers and distribution lines | |
| Owen | The historical development of neutral grounding practices | |
| US6570384B1 (en) | Location of a cable in a dc connection in a bipolar 12-pulse system for transmission of electrical energy by means of high-voltage direct current | |
| US3965394A (en) | Apparatus for protecting a multiphase power transmission line from intermembral faults | |
| Walker et al. | Half‐Megampere Magnetic‐Energy‐Storage Pulse Generator | |
| JP2705219B2 (en) | Ground fault detection protection device | |
| SU649078A1 (en) | Device for melting glaze ice with direct current | |
| CA1079346A (en) | High-voltage network for areas with high rate of icing | |
| SU1201945A1 (en) | Device for automatic shutting of faulted phase in isolated neutral system | |
| SU655019A1 (en) | Arrangement for power supply of consumers | |
| CN1244741A (en) | Tested quantity earth line and phase line selector |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |