KR100685704B1 - A method for calculating power parameters using fuzzy algorithm technology for information visualization of power-receiving/switching boards - Google Patents

Abstract

The present invention relates to a method for calculating a power parameter of a fuzzy algorithm technique for visualizing information of a switchgear. The power parameter calculation method is mainly composed of a fire index calculation method and a power condition index calculation method.

The method of calculating the fire index indicating the degree of fire risk by measuring and analyzing the leakage current, contact failure, transformer maximum temperature, overvoltage and phase loss in the switchgear, the leakage current is measured from the image current transformer (ZCT), Measure the temperature of the temperature sensor installed in each phase to determine the contact failure, and in order to estimate the maximum temperature of the transformer, in the case of the inflow transformer, the temperature of the sensor installed at the top of the transformer oil is measured, and the mold and dry transformer In the case of measuring the temperature of the sensor installed in the winding, measuring the voltage generated from the transformer to determine whether the overvoltage, and measuring the three-phase current to determine whether the phase; Either the temperature measured to determine the leakage current or the contact failure or the temperature generated to estimate the transformer maximum temperature or the voltage generated by the transformer exceeds a predetermined threshold or any one phase of three-phase current. Determining a fire index as state 6 (danger) when no current flows; Calculating a fire index through applying a fuzzy membership function of Dombi if the fire index is not determined as state 6 as described above, and then calculating a fire index through the fuzzy membership function; And if the fire index calculated as above is 0 or less than 0.2, the state 1, 0.2 or more and less than 0.4, state 2, 0.4 or more and less than 0.6, state 3, 0.6 or more and less than 0.8, state 4 and 0.8 or more is determined as state 5 The risk level is increased to the state 5, and the method of calculating the power condition index includes the normality of the current according to the percentage obtained by dividing the largest value of the load currents measured in each phase by the transformer allowable current. Determining an overload; Comparing the current voltage and the distribution voltage of the transformer to determine an undervoltage and an overvoltage; Determining whether or not normal based on a reference power factor (90%) by measuring a load power factor; Determining whether it is normal based on a rated frequency (60 Hz) by measuring a frequency; In the case of single-phase three-wire type, the current unbalance ratio is calculated by multiplying the current difference between two voltage lines by the sum of the currents of both voltage lines and multiplying by two. In the case of three-phase four-wire type, the difference between the currents of both voltage lines is the sum of the currents of both voltage lines. Dividing by and multiplying by 3 to determine whether it is normal; Determining totality by calculating a total harmonic distortion (THD); Calculating an expected value by applying a fuzzy membership function of Dombi and calculating a power condition index through the fuzzy membership function; And if the power condition index calculated as described above is more than 0 and less than 0.2, the state 1, if more than 0.2 and less than 0.4, the state 2, and if more than 0.4 and less than 0.6, the state 3, if more than 0.6 and less than 0.8, the state 4, if more than 0.8 is determined as state 5 The degree of risk is characterized in that it comprises a step indicating that the higher toward the state 5.

Switchgear, information visualization, power parameters, fire index, power condition index, fuzzy algorithm.

Description

A method for calculating power parameters using fuzzy algorithm technology for information visualization of power-receiving / switching boards}             

1 shows a step-by-step maintenance range when the transformer secondary voltage is 110V in the present invention,

2 shows a flowchart of a fire index algorithm according to the present invention,

3 shows a flowchart of a power condition index algorithm according to the present invention.

The present invention relates to a method for calculating a power parameter using a fuzzy algorithm technique for visualization of a switchgear. In particular, the present invention relates to a fire index algorithm and a power condition index algorithm.

Brief description of the background of the prior art in this field is as follows. First, the power condition indicator is a device that reproduces the power condition visually showing the real-time condition of the power by combining 20 parameters such as voltage, current, unbalance, transformer temperature and image current harmonics. By analyzing trends and calculating overload synthesis of power elements, it is a device that can easily determine the power environment at the switchboard through electric fire prediction and waveform capture.

The electricity industry is rapidly changing from the analog age to the digital age, and heavy electric machines in power systems are no exception. Recent developments in digital relays, remote meter reading of digital electricity meters, and the like, it is easy to see that the digitization of heavy electric machines is being rapidly made.

The switchgear was likewise initially operated in analog mode manually, but integration, electronics and digitization have been rapidly progressing since the mid-90s. As a result, a microprocessor has been built into the switchboard, and a lot of data is processed internally. Due to the rapid development of computers, such data storage systems contain so much and diverse data that it is impossible for humans to identify and judge, so many of these data need to be grouped and classified. Information visualization has become a huge new field for developers and users of any system to effectively grasp such a large amount of data, and continues to study the details. Also, by introducing graphic expressions, educational effects can be expected. It is very important for both developers and users to understand and share information more easily, but until recently, the domestic switchgear was only showing the measured value, not the approach of visualizing the information by measuring the measured value of the measuring device.

Contrary to this situation, even small- and medium-sized consumer switchboards are mostly novices or low-level electricians, even if there are no field operators at all. Switchgear panels are becoming more specialized and evolving as the needs of users grow, but effective information delivery to field operators is actually difficult. In addition, since the switchgear is integrated with various equipments, especially the transformer is included, there are always factors that can adversely affect the transformer by overload or insulation deterioration. It is of utmost importance to analyze and prevent these risks before they happen. In the case of the existing switchgear, when the emergency situation occurred, it was difficult for the field operator to easily grasp the status and take action, and thus the risk of the accident was spreading. In order to effectively show the real-time information of the current state of the switchboard and to prevent accidents in advance, the information visualization of the vast measurement data of the switchboard was necessary.

An object of the present invention is to provide a method for calculating a power parameter using a fuzzy algorithm technique for visualizing information of a switchgear in a small and medium sized switchboard.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention and the accompanying drawings.

The power parameter calculation method of the fuzzy algorithm technique for visualizing the switchboard according to the present invention is largely composed of two parts, a fire index algorithm and a power condition index algorithm. Each of these will now be described in detail.

1. Fire index algorithm

Domestic electric fires are gradually increasing every year. Therefore, the switchboard fire index is used to prevent a big accident by expressing the probability of electric fire occurrence to the user.

The fire index algorithm includes five components: leakage current, contact failure, maximum temperature of transformer insulation, overvoltage, and phase loss. It measures the amount of leakage current from the image current transformer (ZCT) and installs a temperature sensor on each phase to capture the temperature rise in case of contact failure. In addition, an important judgment factor is the maximum permissible temperature of the transformer insulation. Overvoltages and open phases can also cause fire.

In order to ensure the safety of electrical installations, it is in principle to insulate everything from the ground except where the wiring and equipment is grounded. If the insulation of the converter / equipment is insufficient, there may be a risk of fire / electric shock due to leakage current. Leakage current must be monitored to prevent fire in a timely manner. Leakage current is measured from the current transformer (ZCT) and the fire risk probability is determined to be 100 [%] when the maximum allowable value is exceeded.

In general, domestic small and medium sized consumer switchgear receives 22.9 [kV] and lowers the voltage to 380 [V] and 220 [V] through a transformer to supply power to customers. Since very high voltage passes through the switchgear, it is very dangerous if contact failure occurs in the connection area in the switchgear. This is because overheating, short-circuit and short circuit, and arc may occur due to poor contact area. This contact failure is measured by a temperature sensor. Like leakage current, if the sensor measures temperature above the reference temperature, it is determined as 100% fire risk.

The transformer overload judging standard for domestic distribution allows the short-term rating up to 130 [%]. However, for efficient and economical use of transformers, short-term overloads must be taken into account, and the ranges in which the transformers cause abnormal life losses will have to be set. International regulations such as IEEE, IEC, JEC, etc. suggest the maximum allowable temperature of insulation by type of insulation and apply differently in case of short overload of 1 ~ 2 hours. In the present invention, the criterion for determining the abnormal life loss of the transformer is regarded as the allowable temperature of the transformer insulator.

On the other hand, there are two types of typical transformers: mold and inflow. In the case of an inflow transformer, the hot spot temperature can be estimated from the measured top-oil temperature by installing a sensor at the top of the transformer oil. Dry transformers can also be equipped with sensors on the windings to estimate the winding hottest points. If this estimated maximum temperature exceeds the acceptance criteria, a fire risk index warning is given.

There are many causes of overvoltages in the system, such as lightning strikes, line accidents, breaker openings or breakdowns, nonlinear / linear resonances, sudden changes in load, and capacitor switching. The high voltage across the line breaks the insulation of the winding and can eventually burn out. However, since it is less likely to actually occur because it is protected by an arrester, considering the possibility of a fire, the overvoltage is also an item that should be watched by a practical user of the switchgear since the insulation may be destroyed by a single instantaneous overvoltage. In the present invention, when the overvoltage of 130 [%] or more of the rated secondary voltage occurs, the fire risk probability 100 [%].

Lastly, if an open phase occurs in three phases, an overcurrent can flow, and the risk of fire is very high. Therefore, an open phase is detected and used as a fire index. The current of each phase is measured, and if no current flows, it is determined to be an image.

In the present invention, the threshold values are set for each of these five elements. Any of the five factors were considered to have a very high risk of fire if the threshold was exceeded. The limit values for the fire index data for each element are shown in Table 1.

The fire index algorithm (also referred to as 'SS fire index algorithm') of the present invention consists of the following steps.

1-1. Leakage Current Calculation Step

Unconditional risk determination (i.e. 1) when I _limit = 100 mA

Leakage current = Leakage current / Reference value (100mA) → Leakage current setting value can be changed according to the reference

1-2. Defective contact stage

Unconditional risk determination if T _limit = 80 ° C (ie, determined as 1)

Poor contact temperature = Measuring temperature / Reference value (80 ℃) → Poor contact set point can be changed according to the standard

1-3. Transformer temperature measurement step

1) Insulation maximum allowable temperature measurement algorithm (in case of inflow type)

end. Class A: 105 ℃

Limit top oil temperature: 105 ℃ -15 ℃ = 90 ℃

① Normal

Step 1: When the top oil temperature is below 39 ℃

Step 2: When the top oil temperature is 40 ~ 49 ℃

Step 3: When the top oil temperature is 50 ~ 59 ℃

② Caution

If step 4 is reached: the message “insulation paper may deteriorate”

Stage 1 (Alarm): When the highest oil temperature is 60 ~ 69 ℃

Stage 2 (Caution): When the oil temperature of the uppermost part is 70 ~ 79 ℃

Stage 3 (Note): When the top oil temperature is 80 ~ 89 ℃

Stage 4 (Danger): When the highest oil temperature is above 96 ℃

I. E class: 120 ℃

 Limit top oil temperature: 120 ℃ -15 ℃ = 105 ℃

① Normal

Step 1: When the top oil temperature is below 44 ℃

Step 2: When the top oil temperature is 45 ~ 59 ℃

Step 3: When the top oil temperature is 60 ~ 74 ℃

② Caution

If step 4 is reached: the message “insulation paper may deteriorate”

Stage 1 (Alarm): When the highest oil temperature is 75 ~ 84 ℃

2nd step (Caution): When the highest oil temperature is 85 ~ 94 ℃

Stage 3 (Note): When the top oil temperature is 95 ~ 104 ℃

Stage 4 (Danger): When the highest oil temperature is above 105 ℃

2) Insulation maximum allowable temperature measurement algorithm (for mold and dry)

end. Class B: 130 ℃

Limit winding temperature: 130 ℃ -20 ℃ = 110 ℃ (where 20 ℃ is the margin of difference from the hottest point of winding based on IEC 60076-11)

① Normal

Step 1: When the winding temperature is below 49 ℃

Step 2: When the winding temperature is 50 ~ 64 ℃

Step 3: When the winding temperature is 65 ~ 79 ℃

② Caution

When step 4 is reached: the message “insulation deterioration possible” is output

Stage 1 (Alarm): When winding temperature is 80 ~ 89 ℃

Step 2 (Note): In case of winding temperature is 90 ~ 99 ℃

Step 3 (Note): In case of winding temperature is 100 ~ 109 ℃

Stage 4 (Danger): When the winding temperature is above 109 ℃

I. Class F: 155 ℃

Limit average winding temperature: 155 ℃ -20 ℃ = 135 ℃ (where 20 ℃ is the margin of difference from the hottest point of winding based on IEC60076-11)

① Normal

Step 1: When the winding temperature is below 69 ℃

Step 2: When the winding temperature is 70 ~ 84 ℃

Step 3: When the winding temperature is 85 ~ 104 ℃

② Caution

If step 4 is reached: the message “insulation paper may deteriorate”

Stage 1 (Alarm): When winding temperature is 105 ~ 114 ℃

Step 2 (Note): In case of winding temperature is 115 ~ 124 ℃

Step 3 (Note): When the winding temperature is 125 ~ 134 ℃

Stage 4 (Danger): When the winding temperature is above 135 ℃

All. Class H: 180 ℃

Limit average winding temperature: 180 ℃ -20 ℃ = 160 ℃ (where 20 ℃ is the margin of difference from the hottest point of winding based on IEC60076-11)

① Normal

Step 1: When winding temperature is below 60 ℃

Step 2: When the winding temperature is 90 ~ 109 ℃

Step 3: If the winding temperature is 110 ~ 129 ℃

② Caution

When 4 levels are reached: “Insulation paper deterioration possible” message output

Stage 1 (Alarm): When winding temperature is 130 ~ 139 ℃

Step 2 (Caution): In case of winding temperature is 140 ~ 149 ℃

Step 3 (Note): When the winding temperature is 150 ~ 159 ℃

Stage 4 (Danger): When winding temperature is over 160 ℃

Table 2 shows limit values of the top oil temperature and the winding temperature for each type of insulation.

1-4. Overvoltage Measurement Steps

Overvoltages are divided into three phases:

① Stage 1: Normal

② Step 2: Caution

③ Stage 3: Risk

And one example of the maintenance range of the transformer secondary voltage is shown in FIG. Fig. 1 shows the maintenance range of the transformer secondary voltage when the secondary voltage is 110 volts. The first stage is 110 to 121V, the second stage is 110 to 132V, and the third stage is 110 to 143V.

If the secondary voltage is 220 volts, 380 volts and 440 volts can also be represented in the same way. In other words, if the secondary voltage is 220 volts, the first stage is 220 to 242V, the second stage is 220 to 264V, and the third stage is 220 to 286V. If the secondary voltage is 380 volts, the first stage is 380 to 418V, 2 The stage is 380 ~ 456V, the third stage is 380 ~ 494V, and if the secondary voltage is 440 volts, the first stage is 440 ~ 484V, the second stage is 440 ~ 528V, and the third stage is 440 ~ 572V.

1-5. Phase determination step

The voltage of each phase is measured, and if it is 0 V, even one phase is determined as an image. The case of phase loss cannot be staged, and only two outcomes are shown.

1-6. Fire index algorithm driving stage

In the present invention, the threshold values are set for each of the above five elements. Any of the five factors is considered to have a very high risk of fire if the threshold is exceeded. The limit values for each element are shown in Table 1. 2 shows a flow diagram of the fire index algorithm. The degree of danger is expressed for each state, and the probability of fire increases as the state goes from state 1 to state 5. State 6 is a fire alarm level.

In the present invention, a fuzzy membership function is also applied to address the uncertainty of the boundary of the limit of each element. In order to establish more effective membership degree, Dombi's proposed S-shaped membership function is used. This method has the advantage that the user can set the degree of belonging desired by adjusting the coefficients. If the threshold value is not exceeded, the expected value is obtained by substituting each data into a fuzzy membership function proposed by Domby according to the flowchart of FIG. 5. Dombi's membership function is defined as in Equation 1.

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

Each calculated μ (x) is multiplied by the appropriate weight w to derive the result. Equation 2 expresses the fire risk index.

Where s is the probability of fire hazard, w _i is the weight of the i th data, μ _i (x) is the expected value of the i th data, and x _i is the input value of the i th data.

If any one of these parameters exceeds the threshold, it is determined to be 1, that is, an unconditional risk. Otherwise, it is determined by multiplying the weights.

Rule 1

If any one of the five parameters exceeds the maximum threshold, a fire hazard index of 100% is determined.

② Rule 2

Rule 1 If not the situation, each parameter value is converted into a percentage and summed, divided by 5.

③ Rule 3

Each parameter is converted into a percentage by the following formula. The transformer temperature is obtained by equation (3).

The formula used here varies from insulation to insulation. The remaining parameters, leakage current, faulty connection, overload voltage are converted into percentages, and if the phase is normal, the expected value is 0, and the phase is 1.

1) membership function

① Leakage current

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

② Poor contact

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

③ transformer temperature

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

④ overvoltage

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

⑤ Image

The open phase is 0 or 1.

2) Setting each parameter coefficient

Each of Tables 3 to 7 shows the set values of each parameter according to the type of transformer (inflow, mold, dry) and the type of insulator.

Table 3 shows the case of an inflow type A insulator. Table 4 shows the case of the inflow, type E insulation.

Table 5 shows the case of mold, dry type B insulation.

Table 6 shows the case of mold and dry, Class F insulation.

Table 7 shows the case of mold and dry, Class H insulation.

3) Defuzzy (Derived)

If any of these parameters exceeds the threshold, it is determined as state 6. In this case, the risk of fire is 100%. And the resulting equation is finally the same as Equation 8.

From the result obtained by this formula, a final decision is made in the following steps.

State1: 0 ≤ x <0.2

State2: 0.2 ≤ x <0.4

State3: 0.4 ≤ x <0.6

State 4: 0.6 ≤ x <0.8

State5: 0.8 ≤ x

2. Power Condition Index Algorithm

Among the most useful data for operating switchboards are electricity rates and quality data. In other words, the user is generally curious about the amount of power and the electrical quality of the device. The power condition index aims to show the most useful data for switchboard managers in this respect. Therefore, in the present invention, the power condition is composed of voltage, current, power factor, frequency, unbalance, and voltage distortion.

First, the current value flowing in the secondary side of the transformer is measured by CT and overload current is shown at a glance by expressing not only the normal current but also the overload current in percentage form. Overload, in other words, is the utilization of the transformer. However, considering load unbalance, Equation 9, which divides the largest phase current by the transformer rated current, is defined as the maximum utilization K ₀ .

는 변압기 허용전류, I_a, I_b, I_c는 a, b, c 각 상의 전류이다.here,

Is the allowable current of the transformer, I _a , I _b , I _c is the current of each of a, b, c phase

Table 8 shows the voltage maintenance range of the domestic distribution system and is based on Article 18 of the Enforcement Rule of the Electricity Business Act. If the reference voltage is out of the maintenance range, display it as normal, caution, and check. For example, if the secondary distribution voltage of the transformer is 220 volts, it is determined as state 1 (normal) if the current voltage is between 213 and 227 volts, and if it exceeds state 1 between 207 and 233 volts, then state 2 (caution) If it is lower than 207 volts or higher than 233 volts, it is determined as state 3 (check required).

At present, the load factor must be maintained at 90 [%] or higher in Korea. The reason is that if the power factor is maintained at 90 [%], the electricity rate will not be penalized, and this 90% is collectively referred to as the reference power factor. In order to maintain the standard power factor, an appropriate capacity capacitor should be installed for each facility, but it should be opened and closed at the same time as the facility. At this time, the user is required to install a part of a condenser or a collective opening and closing device so as not to have a forward power factor. In the algorithm, power factor 100 [%] ~ 90 [%] (reference power factor) is displayed as normal, 90 [%] ~ 70 [%] is indicated as caution status, and when it falls below 70%, an alarm sounds and a warning message is displayed. Outputs If the power factor is reached, an alarm is sounded and a message such as 'block the capacitor' is output.

Unbalance or imbalance is defined as the deviation of the current of each phase with respect to the average current of all three phases and can be calculated by Equation 10. Alternatively, this current imbalance can be defined using the symmetrical component, which is expressed by the ratio of the inverse component (I ₂ ) to the normal component (I ₁ ). The definition by the symmetry component is shown in Equation 11.

Equation 2 was used to calculate the current unbalance of the switchgear transformer. Domestic unbalance rate is regulated not to exceed 30 [%] for 3-phase 4-wire and 40 [%] for single-phase 3-wire. Therefore, set the unbalance rate of 30 [%] for three phases and the unbalance rate of 40 [%] for single phases as the limit and display it.

Finally, looking at frequencies, the main cause of frequency fluctuations is the discrepancy between supply and demand. If there is a shortage of supply, the frequency will drop, and if oversupplyed, the frequency will rise. If there is a customer with a load sensitive to disturbance, a stable voltage with a constant frequency and magnitude is required, and if the rated frequency is 60 [Hz], the fluctuation limit range is defined as ± 0.1 ～ ± 0.3 [Hz]. Therefore, set ± 0.3 [Hz] as the threshold and visually display the change in frequency.

Most sources of harmonic current are generated by equipment using power electronics. As described above, unlike the conventional analogue switchgear, the switchgear has recently been electronicized and digitalized, and thus, power electronic devices are used. Harmonics are frequencies that have an integral multiple of the fundamental wave, and are usually numerical values representing the quality of the distortion wave and can be represented by total harmonic distortion (THD) and harmonic content. According to the Korea Electric Power Corporation's electrical supply agreement, the voltage distortion rate is 3 [%] for customers supplied from substations with underground lines and overhead lines of 66 [kV] or less. Therefore, in the present invention, the voltage distortion of 3 [%] is set as a threshold and visually displayed.

The power condition index algorithm focuses on how effectively and visually the power state is represented to the user. Therefore, unlike the fire algorithm, the fact that exceeding the threshold is not immediately determined as a dangerous state, but is determined by combining all five factors. In the same way as the fire index, the expected value for each data is obtained and the status is displayed.

2-1. Current (Overload Current) Measurement Step

The utilization of the transformer is expressed by Equation 12.

The actual maximum load current is shown in Equation 13.

Therefore, on the basis of this maximum current, it is compared with the largest value among the load currents measured in each phase to determine whether it is overloaded.

① Normal

가 69% 이하인 경우: 1단계

Is less than or equal to 69%: Step 1

가 70~79% 인 경우: 2단계

Is 70-79%: Step 2

가 80~89%인 경우: 3단계

Is 80-89%: Step 3

가 90~99%인 경우: 4단계

Is 90-99%: Step 4

Here, the current of each phase is an average value of 5 minutes.

② overload

가 100~109%인 경우: 1단계

Is between 100 and 109%: Step 1

가 110~119% 인 경우: 2단계

Is 110-119%: step 2

가 120~129%인 경우: 3단계

Is 120-129%: step 3

가 130~140%인 경우: 4단계

Is 130-140%: Step 4

2-2. Reference voltage (undervoltage, overvoltage) measurement step

The reference voltage is determined by the secondary distribution voltage holding range.

① Stage 1: Normal

② Step 2: Caution

③ Stage 3: Risk

When the 3rd stage is reached, the message "Caution of voltage rise (voltage drop) occurs."

The voltage range of the transformer primary voltage ranges from 12,800V / 21,850V to 13,500V / 23,350V for the first stage, 12,000V / 20,800V to 13,800V / 23,800V for the second stage, and out of two stages. When the transformer secondary voltage is 110 balls, the holding range is 107V to 113V in the first stage, 104V to 116V in the second stage, and out of two stages in the third stage.The maintenance range is 1 when the secondary voltage of the transformer is 220 volts. The stages range from 213V to 227V, the second stage is from 207V to 233V, the third stage is out of two stages, and when the transformer secondary voltage is 380 volts, the holding range is 361V to 391V for the first stage, The third stage represents the range outside of the second stage, and the holding range when the transformer secondary voltage is 440 volts is 427V to 453V in the first stage, the 414V to 466V in the second stage, and the outside of the second stage.

2-3. Step of measuring power factor

The ground / truth is judged based on the base power factor (90%). (+) Is the earth and (-) is the truth.

① Normal

Power factor = +-100 to 96%: 1 step

     = +-95 to 91%: 2 levels

② Caution

Power factor = +-90 to 81%: 1 step

     = +-80 to 71%: 2 levels

     = +-70% or less: 3 levels

2-4. Unbalance rate calculation step

Calculation of unbalance by current in each phase (single phase: 40%, three phase: 30%)

1) Single phase 3-wire

Marginal unbalance rate: 40%

= 29% or less: Tier 1

= 30-39%: Tier 2

= 40% over: step 3

2) 3-phase 4-wire

Marginal unbalance rate: 30%

= 19% or less: Tier 1

= 20-29%: Tier 2

= 30% over: step 3

2-5. Frequency measurement step

Monitor the constant frequency (60Hz), measure and mark the frequency, and see 1 if it exceeds ± 0.3 [Hz].

2-6. Total Voltage Distortion (VTHD) Measurement Steps

The total voltage distortion is calculated according to equation (14).

Where V _n is the effective value of the n th harmonic voltage,

V ₁ : Effective value of fundamental wave voltage

If V _THD is over 3%, it is reported as 1 (over regulation), and 0% ~ 3% is displayed step by step.

2-7. Driving stage of power condition index algorithm

1) membership function

① Voltage calculation step

Where V _d is the rated voltage and λ is the minimum value.

② Frequency calculation step

Where F _d is the rated frequency [60 Hz] and λ is the minimum value.

③ Current

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

④ Reference power factor

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

⑤ unbalance rate

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

⑥ V _THD

Where a is the lower limit of the interval, b is the upper limit of the interval, λ is the slope of the curve, and v is the refraction point.

2) Selection step of each parameter coefficient

Table 9 shows the case where the secondary reference voltage is 110V.

Table 10 shows the case where the secondary reference voltage is 220V.

Table 11 shows the case where the secondary reference voltage is 380V.

Table 12 shows the case where the secondary reference voltage is 440V.

3) Defuzzy stage (derived result)

The resulting value is obtained by the equation (21).

From the result obtained by this formula, a final decision is made in the following steps.

State1: 0 ≤ x <0.2

State2: 0.2 ≤ x <0.4

State3: 0.4 ≤ x <0.6

State 4: 0.6 ≤ x <0.8

State5: 0.8 ≤ x

3 shows a flowchart of the power condition index algorithm.

As such, the present invention may be variously modified and may take various forms, and only the specific embodiments thereof are described in the detailed description of the present invention. It is to be understood, however, that the present invention is not limited to the specific forms mentioned in the detailed description of the invention, but rather includes all modifications, equivalents, and substitutions within the spirit and scope of the invention as defined by the appended claims. It should be understood to do.

According to the embodiment of the present invention, a power condition algorithm that complexly calculates 40 or more power parameters can provide users with easy and safe operation by analyzing and providing three-dimensional analysis of current and DB of real-time power load in a switchgear.

In addition, the analysis of 40 major power parameters by the implementation of the present invention to indicate the normal 100% and the maximum index of 700% to present the current value of the live actual load state intelligent safety function indicator to present accurate safety management index index can do.

In addition, through the present invention, a fuzzy membership function was applied to deal with the uncertainty of the boundary of the acceptance criteria of each element, and the S-shaped membership function proposed by Dombi was used to set the degree of effective membership. The present invention has the advantage that the user can set the degree of belonging desired by adjusting the coefficients.

Claims (2)

In the method of calculating the fire index indicating the degree of fire risk by using the fuzzy algorithm technique by measuring and analyzing the leakage current, contact failure, transformer maximum temperature, overvoltage, and phase loss in the switchgear, The leakage current is measured from the image current transformer (ZCT), the temperature of the temperature sensor installed in each phase to determine whether the contact failure, and the top of the transformer oil in the case of the inflow transformer to estimate the maximum temperature of the transformer Measures the temperature of the sensor installed in the sensor, and in the case of the mold and dry transformer, measures the temperature of the sensor installed in the winding, measures the voltage generated by the transformer to determine whether the overvoltage exists, and the three-phase current to determine the phase Measuring; Either the temperature measured to determine the leakage current or the contact failure or the temperature generated to estimate the transformer maximum temperature or the voltage generated by the transformer exceeds a predetermined threshold or any one phase of three-phase current. Determining a fire index as state 6 (danger) when no current flows; Calculating a fire index through applying a fuzzy membership function of Dombi if the fire index is not determined as state 6 as described above, and then calculating a fire index through the fuzzy membership function; And If the fire index calculated as above is more than 0 and less than 0.2, state 1, if more than 0.2 and less than 0.4, state 2, if more than 0.4 and less than 0.6, state 3, if more than 0.6 and less than 0.8, state 4, and if more than 0.8, state 5 is determined. The degree comprises a step indicating that the state increases toward the state 5, 100 mA is set as the threshold reference value of the leakage current amount, In order to determine whether the contact failure is set to 80 ° C as a limit reference value of the temperature of the temperature sensor installed in each phase, In case of inflow transformer type A insulator, 90 ° C is set as the threshold value of the measured temperature to estimate the maximum temperature of the transformer. Normal 2 state, 50 ~ 59 ° C, normal 3 state, 60 ~ 69 ° C, attention 1 state (alarm), 70 ~ 79 ° C, attention 2 state (attention) 80 ~ 89 ° C In 3 states (Caution), if it is over 90 ° C, it is judged as 4 states (Hazard) In case of inflow transformer type Insulator, 105 ° C is set as the limit value.If the temperature at the top is less than 44 ° C, it is in normal 1 state, and if it is 45 ~ 59 ° C, it is in normal 2 state, and if it is 60 ~ 74 ° C, Normal 3 state, 75 ~ 84 ° C, Caution 1 state (alarm), 85 ~ 94 ° C, Caution 2 state (caution), 95 ~ 104 ° C, Caution 3 state (caution), 105 ° C or more Is judged as Caution 4 For mold type or dry type transformer B insulation, set 110 ° C as the limit value and if the winding temperature is below 49 ° C, return to normal 1, if 50 ~ 64 ° C, return to normal 2, 65 ~ 79 ° If it is C, it is in normal 3 state, if it is 80 ~ 89 ° C, it is in caution 1 state (alarm), if it is 90 ~ 99 ° C, it is in caution 2 state, and if it is 100 ~ 109 ° C, it is in caution 3 state (notice), 110 ° If it is C or higher, it is judged as attention state 4 (danger). In case of molded type or dry transformer class F insulation, 135 ° C is set as the limit value.If the temperature of winding is less than 69 ° C, it is in normal 1 state, and if it is 70 ~ 84 ° C, in normal 2 state, 85 ~ 104 ° If it is C, it is in normal 3 state, if it is 80 ~ 89 ° C, it is in caution 1 state (alarm), if it is 90 ~ 99 ° C, it is in caution 2 state, and if it is 100 ~ 109 ° C, it is in caution 3 state (notice), 110 ° If it is C or higher, it is judged as attention state 4 (danger). In case of mold type or dry transformer class H insulator, 160 ° C is set as the limit value.If the winding temperature is below 60 ° C, it is in normal 1 state, and if it is 90 ~ 109 ° C, in normal 2 state, 110 ~ 129 ° C to steady state 3, 130 to 139 ° C to attention 1 state (alarm), 140 to 149 ° C to attention 2 state (attention) 150 to 159 ° C to attention 3 state (caution), 160 ° If it is over C, it is judged as attention state 4 (danger). Fire index calculation method, characterized in that 130% of the rated secondary voltage is set as the threshold reference value of the voltage generated in the transformer to determine whether the overvoltage. In the method of calculating the power condition index by using the fuzzy algorithm technique to measure and analyze whether the current in the switchgear overload, voltage, power factor, frequency, current unbalance rate and the overall voltage distortion ratio, to provide to the switchgear manager, Determining a normal or overload of the current according to a percentage obtained by dividing the largest value of the load currents measured in each phase by the transformer allowable current; Comparing the current voltage and the distribution voltage of the transformer to determine an undervoltage and an overvoltage; Determining whether or not normal based on a reference power factor (90%) by measuring a load power factor; Determining whether it is normal based on a rated frequency (60 Hz) by measuring a frequency; In the case of single-phase three-wire type, the current unbalance ratio is calculated by multiplying the current difference between two voltage lines by the sum of the currents of both voltage lines and multiplying by two. In the case of three-phase four-wire type, the difference between the currents of both voltage lines is the sum of the currents of both voltage lines. Dividing by and multiplying by 3 to determine whether it is normal; Determining totality by calculating a total harmonic distortion (THD); Calculating an expected value by applying a fuzzy membership function of Dombi and calculating a power condition index through the fuzzy membership function; And If the power condition index calculated as above is 0 or less than 0.2, the state 1, 0.2 or more is less than 0.4, state 2, 0.4 or more is less than 0.6, state 3, 0.6 or more is less than 0.8, state 4, 0.8 or more is determined as state 5 The degree comprises a step indicating that the state increases toward the state 5, The percentage obtained by dividing the largest value of the load currents measured by each phase by the transformer allowable current is 69% or less, in normal 1 state, 70-79% in normal 2 state, and 80-89% in normal 3 state, 90 If it is ~ 99%, it is normal 4 state, if it is 100 ~ 109%, it is overload 1 state, if it is 110 ~ 119%, it is overload 2 state, if it is 120 ~ 129%, it is overload 3 state, and if it is 130 ~ 140%, it is overload 4 state. , If the distribution voltage of the transformer is 110V, if the current voltage is 107 ~ 113V, it is in state 1 (normal); if it is 104 ~ 116V and it is out of the range of state 1, it is in state 2 (caution); if it is lower than 104V or higher than 116V, state 3 Judged as (risk), If the distribution voltage of the transformer is 220V, if the current voltage is 213 ~ 227V, it is in state 1 (normal); if it is 207 ~ 233V and it is out of the range of state 1, it is in state 2 (caution); if it is lower than 207V or higher than 233V, state 3 Judged as (risk), When the distribution voltage of the transformer is 380V, if the current voltage is 361 ~ 291V, it is in state 1 (normal); if it is out of the range of state 1 in 342 ~ 418V, it is in state 2 (caution); if it is lower than 342V or higher than 418V, state 3 Judged as (risk), When the distribution voltage of the transformer is 440V, if the current voltage is 427 ~ 453V, it is in state 1 (normal); if it is 414 ~ 466V and it is out of the range of state 1, it is in state 2 (caution); if it is lower than 414V or higher than 466V, state 3 (Risk), When the load power factor is measured, 100 ~ 96% is in normal 1 state, 95 ~ 91% is in normal 2 state, 90 ~ 81% is in caution 1 state, 80 ~ 71% is in caution 2 state, and is less than 70%. Judging by state 3 The fluctuation limit range of the measured frequency is set to 59.8 to 60.2 Hz, If the current unbalance rate is less than 30% for single-phase three-wire type, it is determined to be normal if it is less than 30%, and if it is more than 40%, it is regarded as a danger.If it is less than 20% for three-phase four-wire type, it is normal, 20 to 29% If it's a warning, if it's 30% or more, And determining that the total voltage distortion is more than 3% when the overall voltage distortion rate is 3% or more.

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