A real-time online overload calculation method for transformer

Abstract

The invention discloses a real-time online overload calculation method for a transformer, comprising the following steps: step S1: performing online load loss calculation according to the online switch position of the transformer and the voltage and current of each system and the basic design data and test data of the transformer; step S2: calculating the top temperature of the transformer oil online; step 3: judging the cause of the large deviation of the online transformer load loss and the condition of related components, and calculating the corresponding overload capacity; step S4: judging the performance of the transformer insulation system, correcting the insulation aging rate, and performing overload correlation calculation; step S5: calculating the corresponding overload capacity according to the set transformer overload target, or inputting the set transformer overload target to calculate the corresponding overload time; performing capacity increase and overload capacity assessment on the transformer to achieve full life management of the transformer; determining the long-term operation and overload capacity of the transformer according to the temperature rise test and temperature rise calculation of the transformer.

Description

Technical Field

[0001] The invention relates to a power system method, and in particular to a real-time online overload calculation method for a transformer. Background Art

[0002] At present, transformers are subject to capacity increase and overload capacity assessment to achieve full life management of transformers. The capacity increase and overload calculation of power transformers are mainly based on the temperature rise test and temperature rise calculation of transformers to determine the long-term operation and overload capacity of transformers.

[0003] According to the relevant principles of the oil-immersed transformer load guideline, the relevant time parameters are determined according to the transformer temperature rise test and the basic parameters of the transformer. The national standard and IEC load guideline stipulate the maximum limit temperature of the winding and the maximum limit temperature of the core for related operation, and the manufacturer's regulations must be referred to. At the same time, the corresponding overload capacity is calculated according to the set ambient temperature.

[0004] Although some technologies are calculated based on the real-time load and cooling capacity of the transformer, there is no online transformer load loss calculation for the corresponding load, no online calculation of cooling power, but the overload curve provided by the manufacturer is used, which cannot accurately reflect the real-time overload capacity of the transformer. At the same time, the operating status of the transformer and the impact of the aging degree of the insulation system on the overload capacity of the transformer are not considered.

[0005] For example, a method for measuring and calculating no-load loss of a transformer disclosed in Chinese patent literature, with publication number CN110824260A, cannot calculate the impact of dynamic operation and insulation aging on the actual load capacity of the transformer. Summary of the invention

[0006] The present invention aims to overcome the problems in the prior art that the traditional transformer power consumption calculation method cannot calculate the load during dynamic operation and the influence of insulation aging degree on the actual load capacity of the transformer, and provides a real-time online overload calculation method for the transformer, so as to provide real-time online capacity increase and overload capacity assessment for the current transformer.

[0007] The above technical problem of the present invention is mainly solved by the following technical solution: A real-time online overload calculation method for a transformer comprises the following steps:

[0008] Step S1: Calculate the online load loss according to the online switch position of the transformer, the voltage and current of each system, and the basic design data and test data of the transformer;

[0009] Step S2: Calculate the transformer oil top layer temperature online based on the real-time ambient temperature cooling mode and the load loss data calculated online, combined with the transformer cooling parameters;

[0010] Step S3: Check the deviation between the top oil layer temperature calculated in real time and the top oil layer temperature actually measured, determine the cause of the large deviation of the load loss of the online transformer and the condition of related components, and calculate the corresponding overload capacity;

[0011] Step S4: judging the performance of the transformer insulation system according to the online insulation analysis data of the transformer, correcting the insulation aging rate, and performing overload correlation calculation to ensure that the online transformer overload calculation can correctly reflect the transformer operating status;

[0012] Step S5: Calculate the corresponding overload time according to the set transformer overload target, or input the set transformer overload time to calculate the corresponding overload capacity.

[0013] Preferably, step S1 includes the following contents:

[0014] The online switch position and the system voltage and current of each online system can provide the capacity of the corresponding system. The load loss in the basic design data of the transformer is referred to, and the load loss in the test data is calculated to obtain a more accurate short-time real-time load loss of the transformer online.

[0015] LDh=f(Vh,Ih) high voltage load;

[0016] LDm=f(Vm,Im) medium voltage load;

[0017] LDl=f(Vl,Il) low voltage load;

[0018] Load loss Ploadloss=f(LDh,Rh)+f(LDm,Rm)+f(LDl,Rl);

[0019] Note: Rh, Rm, Rl are the corresponding losses of high, medium and low, obtained by test or calculation.

[0020] Preferably, step S2 includes the following contents:

[0021] According to the cooling method and cooling parameters of the transformer, the real-time cooling capacity of the transformer is calculated; according to the real-time cooling capacity of the transformer and the real-time load loss of the transformer, the top temperature of the transformer and the hottest temperature of the winding are calculated online; under the cooling methods of oil-immersed self-cooling (ONAN) and oil-immersed air cooling (ONAF), the following calculation formula exists:

[0022] Ptank = cooling capacity of the oil tank

[0023] Pradiators = heat dissipation capacity of the chip (need to distinguish between self-heating and fan heat dissipation)

[0024] Total heat dissipation capacity Pdissipation=Ptank+Pradiators

[0025] Heat change ΔTM=f(Ploadloss,Pradiator+Ptank,Hf / Hs)

[0026] Heat change over time Tt = f(ΔTM)

[0027] Note: Hf is the horizontal center height of the device body, and Hs is the center height of the radiator.

[0028] Preferably, step S3 includes the following contents:

[0029] Check the deviation between the top oil temperature calculated in real time and the measured top oil temperature, determine the cause of the large deviation of the online transformer load loss and the condition of related components, and calculate the corresponding overload capacity; check the deviation between the top oil temperature calculated in real time and the measured top oil temperature; when the deviation is large ((Tt-Tm)> set value, set value ONAN, ONAF can be 5, ODAN, ODAF can be 5-10), verify the deviation of related temperature measuring instruments (<=1), if no problem is found, further verify the online transformer load loss (<=10%), cooling capacity deviation (<=10%), and finally adjust the temperature deviation to be less than 1-3. After the deviation is effectively controlled, calculate the corresponding overload capacity. It is necessary to consider the dynamic change of temperature, take the steady-state value for comparison, and the time is greater than the oil time constant.

[0030] Note: Tm is the measured oil top temperature.

[0031] Preferably, step S4 includes the following contents:

[0032] Based on the online insulation analysis data of the transformer, the performance of the transformer insulation system is judged, the insulation aging rate is corrected, and the overload correlation calculation is performed to ensure that the online transformer overload calculation can correctly reflect the transformer operating status.

[0033] Vl=Vn*Fo

[0034] Vl Insulation aging rate

[0035] Vn Normal insulation aging rate

[0036] Fo and insulation system correlation coefficient

[0037] Based on the online insulation analysis data, quantitative assessment is carried out, correlation calculation is performed, and the Fo value is obtained.

[0038] Preferably, step S5 includes the following contents:

[0039] Input the set transformer overload target, calculate the corresponding overload time, calculate the maximum winding temperature of the current load, then increase the load and overload time, calculate the corresponding maximum winding temperature, and ensure that it meets the manufacturer's maximum winding temperature requirements under the corresponding operating conditions; record the set transformer overload time and corresponding overload capacity.

[0040] K is the overload target. According to the initial load and overload target, and according to different overload times Dt, the top oil temperature and the winding hot spot temperature are calculated. By comparing them with the upper limit of the top oil temperature and the upper limit of the hot spot temperature, the allowable overload time T is calculated.

[0041] T overload time, according to different overload Dk, calculate the top oil temperature and winding hot spot temperature, compare with the top oil temperature upper limit and hot spot temperature upper limit, and calculate the allowable overload target K.

[0042] Therefore, the present invention has the following beneficial effects:

[0043] Conduct capacity increase and overload capacity assessment on transformers to achieve full life management of transformers;

[0044] The long-term operation and overload capacity of the transformer are determined based on the transformer's temperature rise test and temperature rise calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flow chart of online real-time overload capacity calculation of the present invention;

[0046] Figure 2 This is a time diagram for calculating the overload target of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0048] Most existing systems use the IEC60076-7-2018 guidelines to check transformer overload capacity. The present invention further calculates the current transformer capacity increase and overload capacity online, corrects the deviation, and performs the following steps:

[0049] Step 1: Calculate the online load loss based on the online switch position of the transformer and the voltage and current of each system collected online in real time, and refer to the basic design data and test data of the transformer.

[0050] Calculating the system voltage and current corresponding to the online switch position can provide the capacity of the corresponding system. Referring to the load loss in the basic design data of the transformer, and calculating according to the load loss in the test data, a more accurate real-time transformer liability loss can be obtained online.

[0051] Example 180MVA, 220+-10% / 115 / 10.5kV

[0052] According to the test data, we can get

[0053] Rh=0.2357kw

[0054] Rm=0.0572kw

[0055] Rl=0.2784kw

[0056] Online high voltage switch position -8, high voltage current 268.4A, medium voltage current 0A, low voltage current 4723.91ALDh=45 high voltage load

[0057] LDm=0 medium pressure load

[0058] LDl=45 low voltage load

[0059] Calculated Ploadloss = 231.3kW

[0060] Note: Rh, Rm, Rl are the corresponding losses of high, medium and low, obtained by test or calculation.

[0061] Step 2: Calculate the transformer oil top temperature online based on the real-time ambient temperature cooling method and the online calculated load loss data, combined with the transformer cooling parameters.

[0062] Calculate the real-time cooling capacity of the transformer based on the cooling method and cooling parameters of the transformer.

[0063] Based on the real-time cooling capacity of the transformer and the real-time load loss of the transformer, the top oil temperature of the transformer and the hottest temperature of the winding are calculated online.

[0064] Example: ONAN

[0065] Tenv=25℃

[0066] Ptank=61.2kW

[0067] Pradiator=636.8kW

[0068] Ptotalloss=320.3kW

[0069] ΔTM=22.3

[0070] ΔTt=31.4

[0071] Tt=56.4℃

[0072] Step 3: Check the deviation between the real-time calculated oil top temperature and the measured oil top temperature, determine the cause of the large deviation of the online transformer load loss and the condition of related components, and calculate the corresponding overload capacity.

[0073] Check the deviation between the top oil temperature calculated in real time and the actual top oil temperature. When the deviation is large ((Tt-Tm)> set value), verify the deviation of the relevant temperature measuring instrument (<=1). If no problem is found, further verify the load loss of the online transformer (<=10%) and the cooling capacity deviation (<=10%). After the deviation is effectively controlled, perform the corresponding overload capacity calculation.

[0074] Note: Tm is the measured oil top temperature.

[0075] Tm 58℃. The deviation is acceptable. No other parameters need to be checked.

[0076] Calculate the overload capacity as follows:

[0077] Continuous overload 134%

[0078] 30 minutes overload 157%

[0079] 60 minutes overload 143%

[0080] 120 minutes overload 133%

[0081] Step 4: Based on the transformer's online oil chromatography analysis data, determine the performance of the transformer's insulating oil, correct the insulation aging rate, and perform overload correlation calculations to ensure that the online transformer overload calculation can correctly reflect the transformer's operating conditions.

[0082] Vl=Vn*Fo

[0083] Vl Insulation aging rate

[0084] Vn Normal insulation aging rate

[0085] Fo and insulation system correlation coefficient

[0086] According to the online data, there is a low temperature overheating phenomenon. According to the correlation calculation, Fo=1.01

[0087] Step 5: Calculate the corresponding overload time according to the set transformer overload target, or input the set transformer overload target to calculate the corresponding overload time.

[0088] Calculate the maximum winding temperature under the current load, then increase the load and overload time, calculate the corresponding maximum winding temperature, and ensure that it meets the manufacturer's maximum winding temperature requirements under the corresponding operating conditions; record the set transformer overload time and the corresponding overload capacity.

[0089] According to calculation, with an overload of 180%, it can run for 18 minutes.

[0090] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A real-time online overload calculation method for a transformer, characterized in that: The following steps are involved: Step S1: Calculate the online load loss according to the online switch position of the transformer and the voltage and current of each system and the basic design data and test data of the transformer. The load loss is obtained by the sum of the functions of the corresponding losses under high, medium and low voltage loads; Step S2: Calculate the transformer oil top temperature online according to the real-time ambient temperature, cooling method and online calculated load loss data, combined with transformer cooling parameters; calculate the transformer real-time cooling capacity according to the transformer cooling method and cooling parameters; calculate the transformer top oil temperature online according to the transformer real-time cooling capacity and the transformer real-time load loss; Step S3: Check the deviation between the top oil layer temperature calculated in real time and the top oil layer temperature actually measured, determine the cause of the large deviation of the load loss of the online transformer and the condition of related components, and calculate the corresponding overload capacity; Step S4: judging the performance of the transformer insulation system according to the online insulation analysis data of the transformer, correcting the insulation aging rate, and performing overload correlation calculation; Step S5: Calculate the corresponding overload time according to the set transformer overload target, or input the set transformer overload time and calculate the corresponding overload capacity; calculate the maximum winding temperature of the current load, then increase the load and overload time, calculate the corresponding maximum winding temperature, and ensure that it meets the manufacturer's maximum winding temperature requirements under the corresponding operating conditions; record the set transformer overload time and the corresponding overload capacity.

2. A real-time online overload calculation method for a transformer according to claim 1, characterized in that: Step S1 includes the following contents: The online switch position and the system voltage and current of each line provide the capacity of the corresponding system, refer to the load loss in the basic design data of the transformer, and calculate according to the load loss in the test data.

3. The real-time online overload calculation method of a transformer according to claim 2 is characterized in that: The general calculation content of step S1 is as follows: LDh=f(Vh,Ih) high voltage load; LDm=f(Vm,Im) medium voltage load; LDl=f(Vl,Il) low voltage load; Load loss Ploadloss=f(LDh,Rh)+f(LDm,Rm)+f(LDl,Rl); Among them, Rh, Rm, and Rl are the corresponding losses under high, medium, and low voltage states respectively, and the actual data are obtained by experiments or calculations.

4. The real-time online overload calculation method of a transformer according to claim 1 is characterized in that: The general calculation content of step S2 is as follows: Ptank = cooling capacity of the oil tank; Pradiators = chip heat dissipation capacity; it is necessary to distinguish between self-heating and fan heat dissipation; Total heat dissipation capacity Pdissipation = Ptank + Pradiators; Heat change △TM=f(Ploadloss,Pradiator+Ptank,Hf / Hs); The change of heat with time Tt = f(△TM); Tt is the top temperature of the oil; Among them, Hf is the horizontal center height of the device body, and Hs is the center height of the radiator.

5. The real-time online overload calculation method of a transformer according to claim 1 is characterized in that: Step S3 includes the following contents: The deviation between the top oil temperature calculated in real time and the actual measured top oil temperature is checked and after the deviation is effectively controlled, the corresponding overload capacity calculation is performed.

6. The real-time online overload calculation method of a transformer according to claim 1 is characterized in that: In step S3, when the deviation between the real-time calculated oil top temperature and the measured oil top temperature is greater than the set value, the deviation of the relevant temperature measuring instrument is verified. If no problem is found, the online transformer load loss and cooling capacity deviation are further verified.

7. The real-time online overload calculation method of a transformer according to claim 1 is characterized in that: In step S4, the insulation aging rate is obtained by multiplying the normal insulation aging rate by the insulation system correlation coefficient.

Images