The Influence of Vacuum Tube Failure in Downhole Vacuum Starter on Leakage Relay

Influence of Vacuum Tube Failure in Underground Vacuum Starter on Leakage Relay Ma Jun (Pangzhuang Coal Mine, Xuzhou Mining Group Co., Ltd., Xuzhou 221141, Jiangsu, China) respectively introduced the leakage protection functions and working principles of vacuum starter JDB and JY82 leakage relays according to the actual conditions on site. The situation described three kinds of abnormal phenomena generated by a leakage relay (abbreviated as a leak detector) when a vacuum starter fails, and the theoretical analysis of the root cause of the above phenomenon was analyzed in detail.

Vacuum Tube; Leakage Blockage; Detecting Current; Superposition Principle 1 Advantages and Common Faults of Vacuum Starter 11 Advantages of Vacuum Starter Vacuum starter has the advantages of strong breaking capacity, small mechanical vibration, complete protection function, and high safety performance. Therefore, it is widely used in low-voltage power supply systems in coal mines.

12 Common Faults of Vacuum Starter Due to improper use, low quality of maintenance personnel, and some product quality problems, vacuum starters inevitably have various types of failures, which mainly include the following types: poor contact or over-position of the reversing switch, resulting in a switch Single-phase or unable to stop electricity; the contact switch of the trip switch breaks, causing the switch to start difficult or insecure; the vacuum contactor mechanism is blocked or the nested spring is jammed to cause the vacuum tube to break off slowly; the vacuum tube closed cap looses or the vacuum tube leaks coal to cause damage The switch is charged on the load side.

2 Vacuum starter JDB leakage lockout working principle JDB is a motor integrated protection device, it has overload, phase failure, line, leakage lock and other protection functions.

JDB leakage blocking schematic diagram When the motor and its power supply circuit is highly resistive, the leakage current of the power supply Ec flowing out through R, R2 is small, A, B two points in the high-power BG1 is still in the conduction state, the relay J is engaged Allow starter to start.

When the leakage resistance is less than the blocking value, the current flowing through R1, R2 increases, the level between A, B drops, N14 reverses, and C becomes a low level, D! Conduction, BG1 cut off, J no electricity release, its normally open contacts open, does not allow the starter to start.

3JY82 leakage relay working principle The basic circuit composition is as shown.

JY82 leakage relay schematic diagram DC power supply E1 (provided by ZL) in the ZJ formation detection current = EW (R +2 r) leakage resistance, 660V system design value is 11kH; 2r is the sum of the resistance of all components of the entire DC detection circuit except R, Mainly depends on the internal resistance of ZJ, generally 1kH. / (11 +1) = 5mA detection current path is: ZL (ten) * kH + R * Grid - under normal circumstances, R value is relatively large (60kH ~ 300kH) detection When the current is less than 5mA, ZJ does not operate and the feed switch does not trip. When a leakage fault occurs, R decreases, the leveling state flowing through ZJ, the output power/AC point is high, and the SeDt turn-off current is greater than the current, and the WriJ pull-in M-hTQ pull-in feed net switch trips. Achieve leakage protection.

The role of JY82 leakage relay: monitoring the insulation status of the line; realizing reliable leakage protection; able to properly compensate the grid capacity current.

4 Influence of the vacuum starter vacuum conduction on the JY82 leakage relay 41 After the fault occurred, the phenomenon of the JY82 leakage relay occurred. According to the experience in the field, it was found that the abnormal operation of the leakage relay is closely related to the failure of the vacuum tube, and with various types of starters. Different models and different, generally there will be the following phenomena: leakage relays immediately action, feed open and trip, line resistance monitoring value was significantly reduced (usually 14 21kQ), leakage relay does not move, but the test is normal.

The ohmmeter is reverse biased, and the leakage relay does not act before and after the test.

42 Analysis of the reasons 4.2.1 After the vacuum tube conduction on the protection circuit When a certain vacuum tube is turned on, combined with a vacuum tube in the composite figure after conduction, Ec is JDB DC supply voltage Ec = +15V; * The phase voltage of the three-phase reactor is U*=380V; d is the DC voltage after Usk is rectified by the diode; Ei is the DC detection power, Ei =60V; Xl is the inductive reactance of the zero-sequence reactor SK, Xl=100lAft, R2 is the current limiting resistance of the leakage branch (in the electronic card), and the dotted line in R represents the path formed by the connected vacuum tube, the power grid, and the auxiliary contacts of the switch.

4.2.2 Computation and analysis are generated by the same action. Using the principle of superposition, there is the existence of Xl in the circuit, and Ud is calculated according to the theory of “AC current conversion technology”. 180* is determined by the following equation: Equation (3) is the transcendental function For different people, the corresponding zero and related Ud values ​​can be obtained by using the trial method, as shown in Table 1 (ft is taken as three commonly used resistance values).

Substituting (1) for >5mA at this time, the leak detector immediately operates to verify the phenomenon (1).

5mA, at this time the detector does not move, because there is a current through the ZJ, the same current in the ohmmeter, so that the absolute resistance monitoring value decreases to verify the phenomenon (2).

The protection component, Ec=40V, and the polarity of the power supply is opposite to the polarity of the JDB leakage blocking part. It forms the reverse current of the detection loop with Ud by the balance resistance Rp of ZL, that is, the phenomenon (3) occurs. The output voltage E1 of ZL is cut off by the GD on the leakage protection component in DQZBH-300/1140 and will not be discussed here.

Learned from the underground mine site, 80 series vacuum switch vacuum tube conduction, the leakage relay can generally move, for the 120,225 series switch in the case of action is less, only 300 series switch to appear ohmic reverse phenomenon .

At the Beijing Coal Management Cadre Institute, he is currently working in the Electromechanical Zone 3 of the Pangzhuang Coal Mine in Xuzhou Mining Group.

Alloy Steel Submerged Arc Welding Wires

Submerged arc welding (SAW), as the name suggests, is conducted beneath a protective layer or blanket of flux. As the arc is always covered by the layer of flux, it eradicates any sort of radiation from the exposed arcs and also necessity of welding screens. With two variants of the process, automatic and semi-automatic, is one of the widely used welding process used in the process industry. Venus wire, one of the renowned submerged arc welding wire suppliers in India, illustrates the principle and uses of sub arc welding. Let us see them what they are:

Process:

Akin to MIG welding, SAW also employs the technique of formation of an arc between the weld joint and the continuous bare electrode wire. A thin layer of flux and slag are employed to generate protective gas mixtures and to add the required alloys to the weld pool respectively. As the weld proceeds, the electrode wire is released at the same rate of consumption and the excess flux is sucked out through vacuum system for recycling. Apart from shielding the radiation, flux layers also are highly beneficial in avoiding heat loss. The excellent thermal efficiency of this process, around 60%, is attributed to these flux layers. Also SAW process is absolutely free of spattering and does not require any sort of fume extraction process.

Operating procedure:

Alike any other welding procedure, the quality of the weld joints with respect to penetration depth, shape and chemical composition of the weld metal deposited are usually controlled by the welding parameters such as current, arc voltage, weld wire feed rate, and weld travel speed. One of the drawbacks (ofcourse methods are available to counter them) is that the welder cannot have a look on the weld pool and hence the quality of well is entirely dependent on the operating parameters.

Process parameters:

As mentioned earlier, it is only with the process parameters, a welder perfects the weld joint. For instance, in an automated process, the wire size and flux that employed that are suitable for the joint type, thickness of material, and size of the job plays an important role in deciding the deposition rate and bead shapes.

Wire:
Depending upon the requirement of deposition rate and travel speeds following wires can be selected

Twin wire
Multiple wire
Tubular wire
Metal powder addition
Single wire with hot addition
Single wire with cold addition
Flux:
Granular mixture of oxides of several elements such as manganese, titanium, calcium, magnesium, silicon, aluminium, and calcium fluoride are widely used as flux in SAW. Usually the combination is selected such that it provides the intended mechanical properties when it combines with the welding wire. It should also be noted that the composition of these fluxes play a vital role in the operating arc voltage and current parameters. Based on the welding requirement, primarily two types of fluxes, bonded and fused are employed in the process.

Uses:

Every welding method has its own set of applications, which usually overlaps due to scale of economy and quality requirement.

Although SAW can be very well employed for both butt joints (longitudinal and circumferential) and fillet joints, it has few minor restrictions. Owing to the fluidity of the weld pool, slag in molten state and loose layer of flux, butt joints are always carried out in the flat position and on the other hand, fillet joints are done in all positions – flat, horizontal, and vertical.
It should be noted that as long as proper procedures and selection of parameters for joint preparations are carried out, SAW can be successfully carried out for material of any thickness.
It can very well be deployed for carbon steels, stainless steels and low alloy steels and also few non-ferrous alloys and materials, provided the ASME code suggested combinations of wire and flux are used.
SAW finds a permanent place in heavy machine industries and ship building industries for welding heavy sections, large diameter pipes, and process vessels.
With very high utilization of electrode wire and easy automation possibilities, SAW is always one of the most sought after welding process in manufacturing industry.

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