简体中文
Electrical fault phenomena are diverse, 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 these fault phenomena bring complexity to finding faults.
However, the fault phenomenon is the basic basis for finding electrical faults and the starting point for finding electrical faults. Therefore, it is necessary to carefully observe and analyze the fault phenomenon, identify the most important and typical aspects of the fault phenomenon, and clarify the time, location, environment, etc. of the fault occurrence.
1. Direct perception
Some electrical faults can be detected through human hands, eyes, nose, ears and other organs, using touch, see, smell, listen and other methods to directly perceive the abnormal temperature rise, vibration, smell, noise, color change, etc. of the faulty equipment, and determine the faulty location of the equipment.
2. Instrument testing
Many electrical faults cannot be determined by direct human perception, and various instruments and meters need to be used to measure the voltage, current, power, frequency, impedance, insulation value, temperature, amplitude, speed, etc. of the faulty equipment to determine the fault location. For example, by measuring insulation resistance, absorption ratio, and dielectric loss, determine whether the equipment insulation is affected by moisture; Determine short circuit points, grounding points, etc. of long-distance lines through measurement of DC resistance. This article introduces a complete set of electrical fault diagnosis techniques.
1、 Sensory diagnosis
1. Judgment of Abnormal Sound in Power Transformers
Normal operation of the transformer, clear and uniform buzzing sound. The sound of the distribution transformer is abnormal, determine the cause of the fault. High buzzing sound, high pitch, overload or overvoltage.
Intermittent strong gurgling sound, rapid increase in single-phase load. The sound of jingling and hammering made the threaded rod loose. Clapping applause, the grounding wire of the iron core broke.
Intermittent wheezing and poor grounding of the iron core. The winding has a slight short circuit and emits bursts of crackling sound. The winding has a severe short circuit and emits a loud roar.
The high-voltage casing has cracks and emits a high-frequency hissing sound. The high-voltage lead housing flashes and crackles. The low-voltage phase line is grounded, and a loud noise can be heard from afar.
Drop switch tap, poor contact, squeaking sound.
2. Using Semiconductor Radio to Detect Partial Discharge in Electrical Equipment
It is difficult to detect partial discharge during inspection of power transformation and distribution equipment. Carry a pocket radio and tune it to a position without a radio station. Turn up the volume to hear the sound, and the uniform buzzing sound is normal.
If the sound is irregular, there is a loud sound of firecrackers or squeaks, and there is a local discharge nearby. Then turn down the volume and measure one by one near the device.
I heard the sound of firecrackers again, and the tested equipment malfunctioned. The equipment partially discharged and emitted high-frequency electromagnetic waves.
3. Diagnose common faults of electric motors using a listening stick
Use a listening stick to listen and determine motor failure. Hear a continuous clicking sound, and the rotor rubs against the stator. The speed slows down and there is a buzzing sound, and the coil contacts the shell and is grounded.
The speed slows down and there is a noise, and the coil is disconnected and missing one phase. The bearing room was hissing, and the bearing lubricating oil dried up. The bearing part made a gurgling sound, indicating that the bearing was damaged.
4. Knocking method for checking the hollow of the wooden rod body
Patrol inspection of wooden electric poles, with hammering around the pole body. Dangdang has a clear and crisp sound, and the body is hollow with a thumping sound.
5. Checking the Insulation Condition of Generator Set Bearings with a Stripping Head Insulated Wire
During the operation of the generator set, the insulation of the bearings should be carefully inspected. Use a stripped insulated wire, with one end of the wire grounded first and the other end touching the rotating shaft. Gently touch multiple times to carefully observe.
Poor insulation due to spark generation, good insulation without sparks.
6. Judgment of single-phase grounding faults in ungrounded neutral systems
Whoever has the highest three-phase voltage must have a fault in the lower phase.
7. Patrol inspection of power capacitors
Patrol inspection of the capacitor revealed excessive oil leakage and temperature rise. The gurgling sound is abnormal, and there is an internal discharge fault.
8. Using the Charging and Discharging Method to Determine the Quality of Small Capacitors
The quality of small capacitors can be roughly judged by the charging and discharging method. Connect the capacitor to the power supply at both ends and charge for about one minute. Short circuit the two electrodes of the capacitor with an insulated copper wire.
Spark flashing is good, no sparks have been damaged.
9. Identifying the polarity of lead-acid batteries
The polarity of a lead-acid battery is unclear with the positive and negative markings. Distinguish by the color of the pole, with the negative pole being cyan gray and the positive pole being deep brown. The position of the pole is different, depending on the positive pole of the factory label.
The diameter of the pole is different, and the positive pole is thicker and the negative pole is thinner. Break the saw blade to cut the pole, and the harder one is the positive electrode. The pole lead is inserted into a sweet potato, and turning green around the line is the positive electrode.
Connect the two wires of the pole, immerse them in a dilute sulfuric acid solution, and produce a bubble end negative electrode without a bubble end positive electrode.
10. Scraping method for checking whether a single cell battery of a battery is short circuited
The internal short circuit of the battery often occurs in one or two compartments. Whether a single cell battery is short circuited is commonly checked using the scraping method. Connect a thicker copper wire to one pole of a single cell battery,
Hold the other end of the copper wire in your hand and quickly scratch the other end. Blue and white sparks appear, indicating that the inspected document is in good condition. The red spark indicates a lack of power, and there is no spark that has caused a short circuit.
11. Checking the Wiring of Two Element Three Phase Energy Meters by Using the Method of Extracting Phase Voltage
Three phase three wire energy meter, check the voltage of the extracted phase. Under constant load, disconnect the neutral phase voltage line.
Observe the operation of the electric energy meter, and the disc rotates half way forward to ensure correct wiring, otherwise there may be an error in the wiring.
12. Determine whether the internal wire of the microampere meter is disconnected
The micro ammeter coil is on or off, and the multimeter cannot measure. Short the copper green wire to the rear terminal of the microammeter, then shake the microammeter while looking at the pointer on the meter head.
The slow oscillation amplitude is small, and the coil inside the meter is intact. Swinging rapidly and significantly, the coil inside the meter has broken.
13. Analyze and judge the fault based on the melting status of the fuse
Check the condition of the fuse melting and determine the fault inside the circuit. The exposed fuse is fully fused and exploded, causing severe overload or short circuit. The fracture in the middle of the fuse is small, and the normal overload time is long.
Broken near the crimping screw, installation damage not tightened.
14. Identify resistance size based on color ring markings
Finished small resistor with nominal resistance value of color ring. The first ring of the color ring is determined, close to the edge ring of the resistor. The last loop is a deviation, and the reciprocal loop is a multiple.
The remaining color ring resistance ring represents the effective number of resistance values. The color code represents the number, multiplied by the power of ten. Brown red, orange yellow, green blue purple, one two three four five six seven,
Grey eight nine white black is zero, and gold is a negative multiple of two silver.
15. Identification method for inferior aluminum core insulated wires
Plastic insulated aluminum core wire, determine the quality by touching the core skin. The core wire is soft and silver white, with poor quality and a harder color that turns black.
The exterior color is bright and the factory name is inferior, outdated, and without identification. The outer skin core wire contacts tightly, and the low-quality sleeve has a large core and small looseness.
16. Distinguishing the Quality of Incandescent Lamp Bulbs
The quality of incandescent light bulbs can be distinguished by looking at a hand model. Bubble is smooth and clean without sand holes, and the product logo is printed clearly. The glass wick is not skewed, and the tungsten wire hooks are evenly arranged.
The installation of the lamp head should not be tilted, and slight force should not loosen it.
17. Identifying the Quality of Transformer Oil
When viewed from outside the transformer oil, the new oil is usually light yellow. After operation, it turns light red, and the color of the oil deteriorates due to aging. The strength varies with the color, and the color becomes black due to severe carbonization.
The test tube is filled with oil to welcome light, and the good oil is transparent and has fluorescence. There is no blue purple reflection, poor transparency, and foreign objects. Good transformer oil is odorless or has a slight smell of kerosene.
Dry and overheated with a burnt odor, severe aging with a sour taste. If an electric arc is generated in the oil, a smell of acetylene will be detected.
18. Drip detection of motor temperature rise
Measure the temperature rise of the motor and sprinkle a few drops of water on the casing. Only hot air emitted without sound, and the tested motor did not overheat. When emitting hot air, there is a sizzling sound, and the motor overheats and the temperature rises excessively.
19. A Simple Method for Judging the Rotation Direction of a Three-phase Motor Before Installing a Rotor
Motor steering prediction, rotor not installed judgment method. The copper wire is bent into a barrel shape, and the inner diameter of the stator is determined by the barrel diameter. Fix the stator vertically and place the cotton thread bucket in it.
After the bucket stops, it is immediately powered on, and the bucket rotates and turns in a fixed direction.
20. Four level discrimination standard for mechanical strength of motor insulation
The insulation quality of electric motors is measured by their mechanical strength. Sensory diagnosis finger press, four level standard discrimination method. Finger press without cracks, with qualified insulation and a hard feel.
Small cracks occur on time, and the insulation is in a fragile state. Major deformation occurs on time, and the insulation has been damaged and is no longer in use.
21. Hand temperature sensing method for detecting motor temperature rise
The operating temperature of the electric motor is detected by hand temperature sensing method. Do not feel hot when flipping your fingers, and place the back of your hand flat on the machine casing. Long term contact turns hands red, slightly hot at around 50 degrees Celsius.
The hand can stay for two to three seconds, and 65 degrees Celsius is very hot. After touching the hand, it was extremely hot, reaching 75 degrees Celsius. It's unbearable to touch my hand just now, it's already overheated at 85 degrees.
22. The temperature of the insulation part of the low-voltage fuse tube of the hand mold quickly determines which phase is blown
Multiple fuses are arranged on the low-voltage distribution panel. The insulation part of the hand mold melt tube, and the melt of the hot hand melt tube is broken.
23. Hand pull wire method for finding broken core fault points between flexible wires
Single core rubber sheathed flexible wire, middle broken core search method. Grasp the outer skin of the thread with both hands, with a spacing of over 200 millimeters. Simultaneously pull outward with force and carefully examine each section.
The sudden thinning of the wire diameter is the point of core breakage fault.
2、 Instrument diagnosis, test pen
1. The correct grip method when using a low-voltage measuring pen
Commonly used low voltage test pen, master the two grip method for testing. A pen style measuring pen with the palm touching the metal clip. Pinch the middle part of the electric pen holder with your thumb, index finger, and middle finger.
A rotary chisel type measuring pen with a metal cap on the tail of the index finger. Pinch the middle finger of the thumb and ring finger tightly in the middle of the plastic rod. The neon tube has a small window with backlight, and you can observe when facing yourself.
2. Precautions when using a low-voltage measuring pen
When using a low-voltage measuring pen, it should be noted that there should be eight items. Use a ballpoint pen to measure the electric pen, grip the rod with a metal hoop. Carefully inspect the assembly inside the electric pen, and the resistance must be behind the neon tube.
Regularly measure and check the resistance value, which must be greater than one megaohm. A rotary chisel type measuring pen, with the chisel rod covered with an insulating tube. Predict the presence of electricity before use and verify its performance.
The testing operation should be accurate and careful not to touch double lines with the pen tip. The insulation pad is used for electrical testing, and the human body must be grounded. When tested under bright light, the glow of the neon tube is not clear.
3. Determine whether any two wires in an AC circuit are in phase or out of phase using a measuring pen
Measure and judge that two wires are the same but different. Hold one electric pen in each hand, insulate both feet from the ground, touch one wire in each pen, and look at one pen with both eyes. If it is not bright and the same phase is bright, it is different.
4. Distinguishing between alternating current and direct current using a measuring pen
The electric pen measures AC and DC, and AC is bright and DC is dark. The AC neon tube is on all sides, while the DC neon tube is on one side.
5. Distinguishing DC positive and negative electrodes with a measuring pen
Measure the positive and negative poles of the DC, and carefully examine the neon tube of the electric pen. The bright front end is the negative electrode, and the bright rear end is the positive electrode.
6. Measuring the grounding of the positive and negative poles of a DC system using a measuring pen
The DC system of the substation does not light up when the electric pen is touched. If the light is close to the tip of the pen, there is a grounding fault in the positive pole. If the light is close to the grip end, the grounding fault is at the negative pole.
7. Judging single-phase grounding fault of 380/220V three-phase three-wire power supply line
The star connection method is used for three phase wires. When the electric pen touches two bright wires, the remaining one has weak brightness, and the phase wire is soft grounded. If the light almost disappears, there is a metallic grounding fault.
8. Judging the phase failure of the star connected three-phase resistance furnace
The neutral point of the three-phase electric furnace is not charged due to load balance. When the electric pen touches the neon tube, it is determined that the fault is a phase failure.
9. Judge whether the neutral line of the electric light circuit is open circuit
The lighting circuit switch is turned on, and the electric light is not on. Use an electric pen to measure. The neutral line of the phase line is on, and the neutral line of the power supply is disconnected.
10. Testing the quality and polarity of high-voltage silicon stacks
The electric pen is connected to a diode in series, and 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 inside the pen shines, hold the negative end of the silicon pile in your hand.
The neon tube inside the pen does not shine, and the silicon pile is held to the extreme. Swap the silicon stack end in your hand and observe it carefully through both forward and reverse measurements. Both neon tubes lit up and there was a short circuit inside the high-voltage silicon stack.
The neon tube did not light up twice, and there was an open circuit in the high-voltage silicon stack.
11. Correct use of digital induction measuring pen
Digital induction testing pen, correct grip and testing method. Press the tip of the pen end with the index finger, the ring finger with the middle finger of the thumb, and pinch the middle and upper part of the plastic rod, while pressing the electrode with the thumb.
The numerical display screen is backlit and can be viewed when facing oneself. Press the thumb to directly measure and touch the bare conductor being measured. Measure according to the induction breakpoint and touch the wire with outer skin.
Distinguish the neutral line of the phase line and find the broken core point of the phase line.
12. Inspection lamp calibration lighting installation project
After the completion of the lighting project, commonly used inspection lights are calibrated. Disconnect all light switches and remove the phase line melt tube. The upper and lower pile heads of the fuse are connected to the high-power inspection lamp.
Connect the main power switch and check the series circuit of the lamp. If the circuit is normal and the light is not on, there must be a short circuit when the light is on. Correct the fault and verify again until there is no short circuit in the circuit.
Verify each light in the branch and close the light switch separately. The branch short circuit test light is on, and the broken wire fault light is not on. If the test lamp emits dim light, it is normal if the tested lamp is on.
Turn off the light to verify the second one, and similarly, calibrate each light using the same method.
13. Verification of single-phase sockets for inspection lights
Single phase 222 socket, often divided into two holes and three holes. The two holes are in phase on the left, middle, and right, with the ground above the phase on the left, middle, and right.
Single phase 222 socket, cross connect inspection lamp calibration. If the inspection light is connected to the left, middle, and right sides and the light is on normally, it is correct. The open circuit fault light does not light up, and the poor contact light flashes.
After testing the three hole socket, the ground light on the right phase is also on, and the ground light on the left middle is not on, otherwise the wiring is incorrect.
14. Verification of single-phase energy meters using a 100 watt inspection lamp
Measure and calibrate single-phase energy meters, and run a 100 watt bulb once. The constant is removed by 36000, and the theoretical time unit is seconds.
The measured theoretical time difference is good with an error of 2%. More practical reasoning leads to fewer words, and more practical reasoning leads to more words.
15. Check the wiring of three-phase four wire electric energy meters using the bulb nuclear phase method
Three phase four wire energy meter, wiring inspection phase verification method. Two inspection lights are connected in series, and the two outgoing lines cross the contact points: the voltage terminal of a certain component and the current power line of that phase.
If the light is on, it indicates that the wire is connected incorrectly and the voltage and current are different phases. The wiring is correct, the light is not on, and the voltage and current are in phase.
16. Inspection lamp detection of single-phase electric energy meter with phase and neutral wires reversed
Domestic single-phase energy meters with one input and one output wiring. Check the two outgoing lines of the lamp, with one end grounded first, the other end touching the meter terminal, and the right incoming and outgoing lines.
The wiring is correct, the light does not turn on, and the zero line is reversed when the light is on.
17. Check the quality of fluorescent tubes with inspection lamps
The quality of the fluorescent tube is determined by the inspection lamp inspection. The end pins of the lamp tube are connected in series to test the lamp and connected to a 222 power supply. The light is on and the tube is glowing, and the end of the tested tube is still good.
The lamp tube has no glow tube end, and the electron consumption of the filament is exhausted. Repeatedly touching the lamp does not turn on, and the filament at the end of the tube has broken.
18. Check the quality of the ballast for fluorescent lamps using inspection lamps
The fluorescent lamp display is abnormal, check the quality of the ballast. Ballast string inspection light, connected to a 222 power supply. The light is dim red orange, and there is no fault inside the ballast.
There is a short circuit when the light is close to normal, but there is no wire breakage or detachment when the light is on.
19. The inspection lamp determines that there is an inter turn short circuit in the winding of the power transformer
It is difficult to determine the inter turn short circuit in the winding of the power transformer. Secondary winding load interruption, primary winding series inspection lamp. Jump over the 222 power supply, and the turn to turn short circuit light is on.
The filament is slightly red and does not light up, and the winding is normal without short circuits.
20. Check the insulation status of low-voltage motors using inspection lights
Low voltage motor insulation, rough inspection with inspection lamp. Control the motor contactor and cross touch the upper and lower sides of the inspection lamp. The light bulb is not bright at all, and the insulation of the motor is good.
The filament is slightly red and slightly damaged, with normal brightness and severe damage.
21. Inspection light detection for low-voltage three-phase motor power supply open phase operation
The motor is running in phase failure, and the inspection lamp is used to detect each phase. Connect the power contactor or the upper and lower sides of the fuse. The cross contact light of the inspection lamp does not light up, and the tested power supply phase is normal.
The filament turns red and dim, and the contact is burnt and the fuse is broken
