There are various electrical fault phenomena. For example, the same type of fault may have different fault phenomena, and different types of faults may be the same fault phenomenon. The identity and diversity of this fault phenomenon bring complexity to find the fault. . However, the failure phenomenon is the basic basis for finding electrical faults and the starting point for finding electrical faults. Therefore, we must carefully observe and analyze the failure phenomena, find out the most important and typical aspects of the failure phenomena, and find out the time and place of the failure , Environment, etc.

　　1. Direct perception

　　For some electrical faults, you can directly detect abnormal temperature rises, vibrations, odors, sounds, and color changes of the faulty equipment by touching, watching, smelling, and hearing the organs such as human hands, eyes, nose, and ears. Fault location.

　　2. Instrument detection

　　Many electrical faults cannot be determined by the direct perception of people. Instead, they need to use various instruments and meters to measure the voltage, current, power, frequency, impedance, insulation value, temperature, amplitude, speed, etc. of the faulty equipment. Identify the fault. For example, by measuring the insulation resistance, absorption ratio, and dielectric loss, determine whether the equipment insulation is wet; by measuring the DC resistance, determine the short-circuit point and ground point of long-distance lines. This article introduces the recipe for electrical fault diagnosis.

　　一 、 Quick and simple sensory diagnosis

　　1. Judgment of abnormal sound of power transformer

　　Normal operation of the transformer, buzzing clearly and evenly. The sound of the distribution transformer is abnormal, and the cause of the fault point is determined. The hum is louder, overloaded, or overvoltage.

　　Intermittent gurgling, single-phase load increased sharply. The clanging sound of hammering, the penetrating screw has become loose. The applause crackled, and the core ground wire broke.

　　Intermittent snoring, iron core poor grounding. The winding is short-circuited and crackles. The winding is short-circuited severely with a loud roar.

　　The high-pressure casing has cracks and emits high-frequency hissing noise. The high-voltage lead shell flashed and crackled. The low-voltage phase line was grounded, and I heard loud noises all the way.

　　The switch tap was dropped, and the contact made a bad squeak.

　　2, Detection of partial discharge of electrical equipment with semiconductor radio

　　When inspecting the power distribution equipment, partial discharge is difficult to find. Bring a pocket radio and tune to no radio stations. The volume is loud and the buzzing sound is normal.

　　If the sound is irregular, there is a very loud firecracker sound, or there is a loud squeak sound, and there is a partial discharge nearby. Then turn the volume down, and test it one by one near the device.

　　Jiu Fu heard firecrackers again, and the device under test was faulty. The device was partially discharged and emitted high-frequency electromagnetic waves.

　　3.Using the listening stick to diagnose common faults of the motor

　　Use a listening stick to listen and confirm the motor failure. A continuous snoring sound is heard and the rotor rubs against the stator. The speed slows down and the buzz sounds, and the coil hits the shell to ground.

　　The rotation speed becomes slow, and the coil breaks, and there is no phase. The bearing room booed and the bearing lubricant ran dry. The bearing parts rattled, and it was determined that the bearing was damaged.

　　4. Check the hollow of the shaft with a percussion method

　　Inspected the wood pole, hammered around the shaft. Dangdang's crisp sound is good, and the snoring sound is hollow.

　　5. Insulation condition of generator set bearings is tested by using insulated wire

　　When the generator set is running, the bearing insulation is inspected. Insulate the wire with a stripped wire. One end of the wire is grounded first and the other end touches the rotating shaft.

　　Poor spark insulation, good insulation and no spark.

　　6. Judgment of single-phase grounding fault in neutral point ungrounded system

　　Whoever has the highest three-phase voltage, the lower phase must be faulty.

　　7. Inspection of power capacitors

　　Inspect the capacitor, the temperature of the oil leaked from the drum is too high. The cooing sound is abnormal and there is a discharge failure inside.

　　8. Judging the quality of small capacitors by charging and discharging method

　　The quality of the small capacitor is rough judged by the charge and discharge method. Connect the capacitor to the power supply at both ends and charge for about one minute. Use an insulated copper wire and short the two electrodes of the capacitor.

　　Spark sparkle is good, no spark has been damaged.

　　9. Identify the polarity of lead storage battery

　　The polarity of lead battery is not clear. The color of the pole is distinguished, and the negative pole is grayish gray and dark brown. The position of the pole is different, relying on the positive end of the factory label.

　　The pole diameter is different, the positive electrode is thinner than the thick negative electrode. Broken saw blades and poles, the harder one is positive. The pole lead is inserted into the sweet potato, and the green around the line is the positive electrode.

　　Connect the two wires of the pole post and dip it into the dilute sulfuric acid solution to produce a bubble-side negative electrode, without a bubble-side positive electrode.

　　10. Check the battery cell for short circuit by scraping method

　　The internal short circuit of the battery occurs in one or two cells. If the single cell battery is short-circuited, it is commonly used to check the fire. Use a thicker copper wire to connect one pole of the single cell battery.

　　Hold the other end of the copper wire in your hand and quickly scratch the other pole. Blue and white sparks appeared, and the inspected cell was in good condition. Red spark is lack of power, no spark has short-circuited.

　　11. Check the two-phase three-phase electric energy meter wiring by drawing the phase voltage method

　　Three-phase three-wire electric energy meter. With the load unchanged, disconnect the medium-phase voltage line.

　　Watch the power meter running, the disc is turning half slower, the only correct wiring, otherwise the wiring is wrong.

　　12. Determine whether the internal boxing of the microamp meter is broken

　　The micro-amp meter coil is on and off, and the multimeter cannot measure it. After connecting the microamp meter to the terminal post, the copper-green wire is shorted, then shake the microamp meter and look at the pointer of the meter.

　　Slow swing amplitude is small, and the coil inside the watch is intact. Quick and large swing, the coil in the watch has been disconnected.

　　13. Analyze and judge the fault according to the fuse blowout condition

　　Look at the fuse blown condition and judge the fault in the line. The exposed fuse is fully blown, severely overloaded or short-circuited. The fracture in the middle of the fuse is small, and the normal overload time is long.

　　The crimping screw is broken nearby, and the installation damage is not compressed.

　　14.Identify the resistance according to the color circle mark

　　Finished small resistor, nominal resistance value of color ring. The first ring of the color ring is determined, close to the resistance edge ring. The last loop is the deviation, and the penultimate loop is the multiple.

　　Resistance ring of other color rings, which means the effective number of resistance values. The color of the color scale represents a number, which is a multiple of a power of several tens. Brown red orange yellow green blue purple, one two three four five six seven,

　　Gray, white and black are zero, gold, silver and two negative multiples.

　　15. Identification method of inferior aluminum core insulated wire

　　Plastic insulated aluminum core wire. The core wire is soft silvery white, and the inferior quality is hard and the hair is black.

　　The outer skin color is brilliantly printed, the name is inferior, obsolete and no logo. The outer core wire is in tight contact, and the inferior sleeve has a large core and Komatsu.

　　16.Identify the quality of incandescent bulbs

　　Incandescent bulbs are good or bad. The bubble is smooth and clean without trachoma, and the product logo is clearly printed. The glass wick is not skewed, and the tungsten wires are evenly arranged.

　　The installation of the lamp head is not skewed.

　　17.Identify the quality of transformer oil

　　When viewed from outside transformer oil, new oil is usually pale yellow. After running, it is light red, the oily aging color becomes darker, the intensity varies with different colors, and the charring color becomes black.

　　The test tube holds the oil and looks at the light. Good oil is transparent and fluorescent. No blue-violet reflection, poor transparency and foreign matter. Good transformer oil is odorless, or has a little kerosene smell.

　　The smell of dried and overheated coke, severe aging and sour. If an arc occurs in the oil, it will smell acetylene.

　　18.Dry water detection motor temperature rise

　　When the temperature rise of the motor drops, a few drops of water are sprinkled on the casing. Only the hot air is emitted without sound, and the motor under test does not overheat. When the hot gas is emitted, the motor will overheat and the temperature rises.

　　19. A simple method to determine the steering of a three-phase motor without a rotor

　　Electric motor steering prediction, the rotor is not installed judgment method. The copper wire is bent into a barrel shape, and the inner diameter of the stator is set to the barrel diameter. The stator is fixed vertically, and a cotton bucket is placed in it.

　　After the bucket is stable, it is powered on instantly, and the bucket rotates and turns.

　　20 、 Four-level discrimination criteria for mechanical strength of motor insulation

　　The quality of motor insulation is measured by mechanical strength. Sensory diagnosis finger press, four-level standard discrimination method. There are no cracks when pressed by fingers, and the insulation feels hard.

　　Small cracks occur on time, and the insulation is in a fragile state. Large deformation occurs on time, and the insulation has been stopped.

　　21, Motor temperature rise detection

　　The running temperature of the motor is measured by the feel temperature method. Fingers don't feel hot when you try to push, and the back of the hand is flat on the cabinet. Touching hands for a long time becomes red, and it is slightly hot around 50 degrees.

　　Hold your hand for two or three seconds, sixty-five degrees is very hot. It was very hot after touching it, and it was extremely hot at seventy-five degrees. The hand was just unbearable, and it was overheated at eighty-five degrees.

　　22, the temperature of the insulation part of the fuse of the hand mold low-voltage fuse quickly determines which phase is fused

　　A plurality of fuses are arranged on the low-voltage power distribution panel. Insulation part of hand-molded pipe, melt of hot-hand pipe is broken.

　　23. Find the broken core fault point between flexible cords by pulling the wire method

　　Single-core rubber-sheathed flexible wire, the method of finding the middle broken core. Grasp the outer sheath of the wire with both hands, more than 200 mm apart. At the same time, pull out forcefully and check it carefully section by section.

　　The sudden thinning of the wire diameter is the point of failure of the broken core.

　　Two, test pencil, lamp inspection

　　1. The correct grip when using a low-voltage test pen

　　Commonly use low-voltage test pens to master the test of two grips. Pen-type stylus with the palm touching the metal clip. Forefinger and middle finger of the thumb, pinch the middle of the pen.

　　Rotary chisel type electric pen, the index finger presses the tail metal cap. Middle finger of the thumb and ring finger, pinch the middle of the plastic rod. The neon window is backlit and looks towards you.

　　2. Things to know when using low-voltage electric pen

　　When using a low-voltage test pen, you should know that there should be eight items. Stylus with ballpoint pen, pinch the lever with metal hoop. Carefully inspect the assembly of the electric pen, the resistance must be behind the neon tube.

　　The resistance value must be measured regularly and must be greater than one megohm. Rotary chisel type electric pen with chisel rod covered with insulating tube. Before use, there is a power supply forecast to check whether the performance is good.

　　Test operation should be accurate, be careful not to touch the double line with the pen tip. For the electricity test on the insulation pad, the human body part must be grounded. Testing under bright light, neon tube glow is not clear.

　　3.A stylus pen tests whether any two wires in the AC circuit are in phase or out of phase

　　According to the test, the two wires are the same and different. Each hand holds an electric pen, the two feet are insulated from the ground.

　　4.Differentiating between AC and DC

　　Electric pen test AC and DC, AC bright DC dark. The AC neon tube lights up, and the DC neon tube lights up.

　　5.The difference between DC positive pole and negative pole

　　Test and judge DC positive and negative poles, electric pen neon tube look carefully. Bright front is negative, bright rear is positive.

　　6. The stylus pen measures the positive and negative ground of the DC power system

　　The DC system of the substation does not light up when the electric pen touches it. If the light is near the pen tip, the positive pole has a ground fault. If the light is near the grip end, the ground fault is at the negative pole.

　　7. Judging single-phase ground fault of 380 / 220V three-phase three-wire power supply line

　　Star-connected three-phase wire. The electric pen touches two bright ones, and the remaining one has weak brightness. If there is almost no light, the metal ground fault.

　　8. Judging the phase failure of star-connected three-phase resistance furnace

　　Neutral point of three-phase electric furnace, load balance is not charged. The electric pen touched the neon tube and it was judged that the fault was a phase failure.

　　9. Judging that the neutral line of the electric light line is open

　　The lighting circuit is switched on and the electric light is off. The phase neutral line is on, and the power neutral line is disconnected.

　　10. Detecting the quality and polarity of high voltage silicon stack

　　Electric pen string only has diode, the positive pole is connected to the mains phase line. Hold either end of the silicon stack and touch the metal clip of the piezoelectric pen. If the neon tube in the pen is bright, hold the negative end of the silicon stack in your hand.

　　The neon tube inside the pen is not bright, and the silicon stack in the hand is extreme. Hold the end of the silicon stack for replacement, and observe the front and back. The neon tube was illuminated twice, and a short circuit occurred in the high-voltage silicon stack.

　　For two times, the neon tube was not lit, and the high-pressure silicon stack was open.

　　11. Correct use of digital display induction test pencil

　　Digital display induction test pen, hold the test method correctly. Forefinger press the top of the pen tip, thumb middle finger ring finger, pinch the middle and upper part of the plastic rod, and the thumb takes care of pressing the electrode.

　　The value display is backlit, and you can observe it when you are facing. Press the thumb directly to test and touch the bare conductor to be tested. Press the induction breakpoint to check and touch the sheathed wire.

　　Distinguish the neutral line of the phase line and find the core break point of the phase line.

　　12. Inspection lamp inspection lighting installation project

　　After the lighting project is completed, it is commonly checked by inspection lights. Disconnect all light switches and remove the phase wire melt tube. The upper and lower pile heads of the fuse are connected with high-power inspection lamps.

　　Turn on the main power switch and check the lamp in the series circuit. The normal light of the line is not on, and there must be a short circuit when the light is on. Troubleshoot and recheck until there is no short circuit on the line.

　　Check each lamp on the branch and close the light switches. The branch short circuit inspection light is on, and the disconnection fault light is off. The inspection lamp emits dim light, and the inspection lamp is normal.

　　Turn off the light and check the second one.

　　13. Single-phase socket for inspection lamp inspection

　　Single-phase 220 sockets, often divided into two holes and three holes. The left, middle, and right of the two holes are phases, and the left, middle, and right phases are above the ground.

　　Single-phase 220 sockets, cross-checking inspection lamp check. The left, middle, and right inspection lights are correct. The disconnection fault lamp does not light, and the poor contact lamp flashes.

　　Three-hole socket plus test, the ground light on the right phase is also on, and the ground light on the left middle is off, otherwise the wiring is incorrect.

　　14. Single-phase energy meter

　　Test and calibrate the single-phase electric energy meter. The constant is removed by 36,000, and the theoretical time unit is second.

　　The measured theoretical time difference is 2% better. Do more with less words, and do more with less words.

　　15. Check the wiring of three-phase four-wire electric energy meter by nuclear phase method

　　Three-phase four-wire electric energy meter, wiring check nuclear phase method. Two inspection lamps are connected in series, and the two lead wires cross the contacts: a component voltage terminal and the phase current power line.

　　The light is on, indicating wrong wiring, voltage and current are out of phase. The lights are not on when the wiring is correct, and the voltage and current are in phase.

　　16. The inspection lamp detects that the phase line and neutral line of the single-phase energy meter are reversed.

　　Domestic single-phase electric energy meter, one-in-one-out wiring. Check the two lead wires of the lamp, one of the leads should be grounded first, the other should touch the meter terminal, and the right incoming and outgoing wires.

　　The light is not on when the wiring is correct, and the zero line is reversed when the light is on.

　　17. Inspection lamp detects the quality of fluorescent tubes

　　The quality of the fluorescent tube is checked by the inspection lamp. The end of the lamp tube is used to inspect the lamp, and it is connected to the 220 power supply. The lamp is on and the lamp is glowing, and the end of the tested lamp is not bad.

　　The lamp has no glow tube end, and the filament electronics are exhausted. Repeatedly touched and waited, the filament at the end of the tube was disconnected.

　　18. Ballast for fluorescent lamp

　　The fluorescent lamp is abnormal, and the ballast is good or bad. Ballast string inspection light, connected to 220 power supply. The light is dim red and orange, and there is no fault in the ballast.

　　Liang has short circuit near normal.

　　19. The test lamp judges that the power transformer winding has an interturn short circuit.

　　Power transformer windings, short turns are difficult to judge. The secondary winding is disconnected from the load, and the primary winding is inspected in series. Connected across 220 power sources, the inter-turn short circuit light is brighter.

　　The filament is not reddish, and the winding is normal without short circuit.

　　20. The inspection lamp detects the insulation status of the low-voltage motor

　　Low-voltage motor insulation, rough inspection of inspection lights. The motor contactor is controlled, and the inspection lamp crosses the upper and lower sides. The bulb does not light at all and the motor is well insulated.

　　The filament is slightly reddish and the brightness is normal and bad.

　　21 、 Inspection