US1922125A

US1922125A - Insulator heating circuit

Info

Publication number: US1922125A
Application number: US585608A
Authority: US
Inventors: Alexander N Crowder
Original assignee: Research Corp
Current assignee: Research Corp
Priority date: 1932-01-08
Filing date: 1932-01-08
Publication date: 1933-08-15
Anticipated expiration: 1950-08-15

Description

Aug. 15, 1933, A. N. CROWDER INSULATOR HEATING CIRCUIT Filed Jan. 8, 1932 2 Sheets-Sheet l g. 15, 1933. ANl COWDER 1,922,125

IJNSULATOR HEATING CIRCUIT Filed Jan. 8, 1952 2 Sheets-Sheet 2 4 di? a l U 2@ l Ja j L5 i y' `l Il LL@ ff@ j Patented Aug. l5, 1933 PATENT oFF-ica v 1,922,125 INsULA'roR HEATING ontcurr Alexander N. Crowder, Bound Brook, N. J., as-

signor to Research Corporation, New York, N. Y., a Corporation of New York Application January s, 1932. seriai No; 585,608

l Claims.

This invention relates to a method and device for heating electrical insulators. It is particularly adapted for use in connection Withan electrical system comprising a low voltage circuit which includesresistance and other control units coupled through a step-up transformer to a high voltage circuit which includes elements for producing discharges in gases and high voltage insulators exposed tosaid gases.

The principal object of the invention is the e'icient utilization of the energy dissipated by the current-regulating devices. This object is accomplished by associating with insulators in the high voltage circuit the heat-generating regulating means in the low-voltage circuit.

The invention may be illustrated by describing its application to the art of electrical precipitation. In electrical precipitator installations it is common practice to include a considerable amount of so-called ballasting resistance in the low voltage side of the circuit for the purpose of damping the current surges that are set up when arc-overs occur in the high voltage side of the circuit between the electrodes within the precipitator. The use of such resistance also tends to prevent a condition of resonance in the system which might otherwise f exist due to the inductance and capacity present in such an electrical system. Sometimes it is found necessary to introduce suicient resistance to reduce the voltage available at the low voltage, terminals of the transformer to one-half that supplied by the power lines. At times of arc-over when heavy rushes of current take place, the drop in voltage may be even greater than 50%.

When the amount of resistance provided for the purpose of controlling the electrical conditions in the system is sufcient to bring about an appreciable drop in voltage, considerable of the energy consumed in the system consists oi 12R loss in the resistance units and the usual practice is to dissipate this energy as heat into the surrounding air. rlhis invention is directed toward the economical utilization of this energy.

In electrical precipitators used with gases containing moist and conducting particles, it has been found to be good practice to heat the surface of the high voltage insulators riuhere exposed to the gases to prevent the deposition of conducting particles on this surface. The insulators are commonly heated by placing chambers around them and heating the gas in the chamberswith steam coils. In the present invention, advantage is taken of the fact that (Clo 18S-7) v l electrical energy is being dissipated in the form of heat in the low Voltage side of the precipita-- tor circuit and the resistance units giving oi this heat are placed within the high voltage insulator chambers or within the shells of the insulators themselves, or otherwise associated in heal'. transfer relations with the insulators. Thus the surface of the insulators is maintained at temperatures above the dew point of the gases being cleaned, or otherwise treated.

The invention will be described, by way of example, with reference to the accompanyingr iigures, wherein:

Figure l shows in elevation, partly in section. an assembly of high voltage insulators, including a bushing with electrical heating elements;

Figure 2 is a lplan View through section 2 2 of Figure 1;

Figure 3 shows in side elevation a supporting insulator, such as are used in Aelectrical precipitators, with an electrical heating unit;

Figure 4.- shows diagrammatically the manner in which insulators such as those shown in Figures 1, 2 and 3, when used in an electrical precipitatorcan be heated in accordance with the invention.

In Figures l and 2, 1 is an insulating bushing which covers in more or less gas-tight manner the opening 2 in plate 3, but in which there is a small opening 5 through which a supporting rod l passes to make possible the suspension of the framework below the plate, represented by member 7, from member 6 above the plate.

Member 6 is supported by insulators 8. The inside of bushing 1 is heated by electrical heaters 9 of the air immersion type. Such an assembly of insulators is useful in apparatus for the electrical treatment of gases, and when so considering it, plate 3 represents the top plate of a casing holding the gas to be treated and member 7 represents the framework from which electrodes may be hung in the manner well known to those versed in the art. Connections 10 and 1l are a part of an electrical supply circuit to be described later.

Figure 3 illustrates the use of a supporting insulator in apparatus for the removal of suspended particles from gases in which the insulator is not fully protected from the gas passing through the apparatus and requires heating to prevent the deposition of conducting material upon it. The insulator 12 supports the high voltage busbar l5 from which discharge electrodes, such as lamentary member 23, are suspended within grounded collecting electrodes,

such as pipe 22. A sleeve 17 is placed over the bus bar 15, where it passes through the shell 16 of the precipitator chamber 16 and a torus ring 18 covers the edge of the hole in shell 16' so that the annular opening 14, defined by said sleeve and torus ring, is free from edges which would permit disruptive spark-overs at relatively low voltages. Because of this freedom from sharp edges, the annular opening 14 can be quite narrow and the movement of gas into and out of the insulator box 13 is not great. It is often advisable, however, to heat the gas contained in the insulator box to provide against the deposition of dust in a moist, conducting condition or condensed vapors, on the surfaces of the insulator. The insulator 12 and the gas immediately surrounding it is heated with an electricalresistance unit 19, made up in helical form and maintained in position around the insulator by fastenings 20 which project out from the sides of the insulator box 13. Heating unit 19 is supplied with electric current through conductors 21 which are shown entering the bottom of the insulator box.

In Figure 4, outline 33 indicates in plan view an electrical precipitator for the removal of suspended particles from gases. The insulation for this precipitator is similar to that shown in Figs. 1 and 2. 'Ihe supporting insulators are represented by 28 and gas-tight bushings 3l are shown around rods 24. The resistance units 27 which are for the purpose of heating bushings 31 are connected by insulated wires 29 and 30 to conductors 25 and 26, respectively. As shown, two resistance units are connected in series by connector 30 'for the heating of a single bushing.

Current to heat the resistance units or heaters 27 is secured from the power supply lines through connections 41 and 42. It can be supplied directly to the resistance units through switch 34, or switch 35 can be used to connect the resistance units 31 in series with variable resistance 36 and the low tension winding of transformer 37. The former connection can be used when the installation is being made ready for the treatment of gases and before the transformer and rectifier are placed in service. With the connection through switch 34, full voltage is impressed across each two resistance units, which impresses half "line voltage across each unit. This is a desirable condition when no gas is passing toassist in heating'the bushings 31 and all the heat must be secured from the electrical heaters 27. When the bushings are heated to a satisfactory working temperature, the gas may be allowed to flow through the precipitator and voltage is impressed on the high voltage electrode system of the precipitator. n

To energize the high voltage electrode system, switch 34 is opened and switch 35 is closed. With switch 35 closed, current flows through transformer 37, the current from the high voltage winding of the transformer is rectified by translating device 38 and the resulting unidirectional current is supplied to the high voltage electrodes by conductor 39 which is connected to one of the supporting rods 24.

It is evident that the voltage available across the resistance units l27 within the bushings 31 is less when the transformer 37 and resistance 36 is included in the circuit. This is a desirable condition because less heat is required to maintain the bushings at the proper temperature than is required to bring them up to that temperature; and furthermore, as most gases which require cleaning or conditioning are above atmospheric temperatures, the gases furnislran additional source of heat as soon as they are passed through the precipitator to be cleaned.

Variations in the above circuits will be apparent to those familiar with the operation of electrical precipitation units. The voltage to be impressed on the low-voltage Winding of the transformer can be altered by use of the auxiliary variable resistance 36. Also, to give flexibility to the values of the high voltage current, several taps can be made to the low voltage winding in a manner well known to transformer engineers. Also, the resistor units within the insulator bushings can be connected up variously in series and in parallel so that the voltage across an individual resistance unit can be changed by changing the connections to these units.

The particular arrangements shown in the drawings and described above are merely examples of the principle of the invention, and it will be seen that the invention broadly comprises the lheating of high voltage insulators in a system containing high voltage and low voltage circuits by associating heat-generating regulating means in the low voltage circuit in heat transfer relation with the high voltage insulators, the term insulators being used broadly to denote devices or elements for preventing undesired leakage of current from electrical conductors.

I claim:

1. Apparatus for the treatment of gases with high potential electrical discharges comprising a low voltage circuit, a transformer, a high voltage circuit, insulators in said high voltage circuit and heat-generating means in said low voltage circuit for regulating the current charac` teristics of the system, said means being associated in heat transfer relation with said insulators.

2. Apparatus for the treatment of gases with high potential electrical discharges comprising a low voltage circuit, a transformer, a high voltage circuit, insulators in said high .voltage circuit and resistance elements in said low voltage circuit for regulating the current characteristics of the system, said elements being associated in heat transfer relation with said insulators.

3. Apparatus for the treatment of gases with high potential electrical discharges comprising a low voltage circuit, a transformer, a high voltage circuit, insulators in association with the high voltage conductors of said high voltage circuit, and resistance regulative elements in said low voltage circuit positioned in heat transfer relation to said insulators.

4. Apparatus for the treatment of gases with high potential electrical discharges comprising a low voltage circuit, a transformer, a high voltage circuit, insulators in association with the high voltage conductors of said high voltage circuit, resistance regulative elements in said low voltage circuit positioned in proximity to said insulators, and current switching means adapted to connect a source of low voltage supply with said regulative elements either directly or in series with said transformer.

ALEXANDER N. CROWDER.