CN110460009B - Inverse time limit relay protection setting method for transformer of ferroalloy furnace - Google Patents

Inverse time limit relay protection setting method for transformer of ferroalloy furnace Download PDF

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CN110460009B
CN110460009B CN201910827662.9A CN201910827662A CN110460009B CN 110460009 B CN110460009 B CN 110460009B CN 201910827662 A CN201910827662 A CN 201910827662A CN 110460009 B CN110460009 B CN 110460009B
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protection
transformer
current
ferroalloy
furnace
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CN110460009A (en
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郑伟
李鹏
富钢
巴月娥
杨冶
高贵军
耿全德
殷业鹏
于雷
何润全
曲晗
宋承泽
孙震
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Ansteel Engineering Technology Corp Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/006—Calibration or setting of parameters

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Abstract

The invention provides an inverse time limit relay protection setting method for a ferroalloy furnace transformer, which is suitable for overload protection setting of the ferroalloy furnace transformer and similar electric arc furnace transformers. The model curve has inverse time limit characteristics, can be matched with a variable operation curve of the ferroalloy electric furnace by utilizing the inverse proportion relation between time and current, and does not act during normal production; when in fault, the larger the fault current is, the shorter the action time is, and the better selectivity and rapidity are realized. The service life of the electric furnace transformer is greatly prolonged, the problem of dead zones in the traditional timing protection is solved by using the inverse time limit characteristic of the protection on the basis of not increasing any equipment investment, and meanwhile, the protection is used as the near backup protection of the main protection, so that the equipment can be quickly cut off when in failure, and the method has important significance for prolonging the service life of the equipment.

Description

Inverse time limit relay protection setting method for transformer of ferroalloy furnace
Technical Field
The invention relates to the technical field of energy generation, power supply and power distribution, in particular to an inverse time limit relay protection setting method for a transformer of a ferroalloy furnace.
Background
The iron alloy electric furnace transformer belongs to one kind of ore smelting electric furnace transformer, and because its load characteristic is similar to that of electric arc furnace transformer, the relay protection function of its electric system is the most important technical index for ensuring equipment safety and running stability, especially overload protection. The current main setting calculation method is as follows:
the requirements of table 1 are met by protection and setting calculation which should be set by a transformer of a ferroalloy furnace, which is registered in the handbook of electric power design of iron and steel enterprises, P706.
TABLE 1 setting calculation of iron alloy furnace transformers
Figure BDA0002189302950000011
According to table 1, the overload protection of the transformer uses a fixed time limit with a time of 120s, that is, no matter the transformer is overloaded several times, for example, 1.1 times, 1.2 times, 1.5 times, 2 times, etc., the tripping and alarming time is 120s or more, and the fault can be removed by the quick-break protection action only when the overload multiple reaches 2.5 times or more.
Disclosure of Invention
In order to solve the technical problem in the background art, the invention provides an inverse time limit relay protection setting method for a transformer of a ferroalloy furnace, which is a mathematical model of a relay protection action equation, wherein a model curve has inverse time limit characteristics, can be matched with a variable operation curve of the ferroalloy furnace by utilizing the inverse proportion relation between time and current, and does not act during normal production; when in fault, the larger the fault current is, the shorter the action time is, and the better selectivity and rapidity are realized.
In order to achieve the purpose, the invention adopts the following technical scheme:
an inverse time limit relay protection setting method for a ferroalloy furnace transformer is suitable for overload protection setting of ferroalloy electric furnace transformers and similar electric arc furnace transformers.
When the capacity of the iron alloy electric furnace transformer is not more than 33000kVA, the mathematical curve model is as follows:
Figure BDA0002189302950000021
when the capacity of the iron alloy electric furnace transformer is larger than 37000kVA, the mathematical curve model is as follows:
Figure BDA0002189302950000022
when the iron alloy electric furnace transformer is manufactured with special requirements, namely the allowable overload capacity of the transformer is not 1.3 times or 1.05 times of that of the formula 1 and the formula 2, but other values A, the mathematical curve model is as follows:
Figure BDA0002189302950000023
in the formula:
t-action time of protection;
Iop.k-an action current of the protection device;
In-the iron alloy furnace becomes the rated current of the high-pressure side;
a-the transformer allows long-time overload multiples;
the value of τ is calculated by substituting the data in the following table into equation 3.
Multiple of overload Iop.k/In 1.4 1.5 1.6 2 3 4 8
Corresponding time(s) 10～15 4～8 3～5 1～3 0.5～1 0.2～0.5 0～0.2
Compared with the prior art in the background art, the invention has the beneficial effects that:
1. the invention fills the blank of the industry, and the existing setting of microcomputer relay protection before the operation of the ferroalloy electric furnace has no relevant regulation of national unified standards and regulation specifications, so that the setting of the relay protection mostly uses the traditional fixed time limit protection, or a long-delay inverse time limit curve (3 times of action current, 6s) and the like is randomly selected in a protection device.
2. The service life of the electric furnace transformer is greatly prolonged, the problem of dead zones in the traditional timing protection is solved by using the inverse time limit characteristic of the protection on the basis of not increasing any equipment investment, and meanwhile, the protection is used as the near backup protection of the main protection, so that the equipment can be quickly cut off when in failure, and the method has important significance for prolonging the service life of the equipment.
3. The accuracy is high, and the cost is saved; compared with the traditional calculation method, the inverse time limit characteristic of the action equation not only has quick action, but also has selectivity, and greatly improves the action effect of relay protection.
4. The scheme is simple and easy to understand and realize.
Drawings
FIG. 1 is a plot of the 33MVA and following general characteristic equations for an electric ferroalloy furnace;
FIG. 2 is a graph of the total characteristic equation for an electric ferroalloy furnace 37MVA and above;
FIG. 3 is a plot of the 33MVA and following equations of motion characteristics for an electric ferroalloy furnace;
FIG. 4 is a graph of the equation of the operating characteristics of an electric ferroalloy furnace 37MVA and above;
FIG. 5 is a 110kV power supply system of an iron alloy electric furnace FIG. 1(33000 kVA);
FIG. 6 shows a 110kV power supply system of an iron alloy electric furnace in FIG. 2(37500 kVA).
Detailed Description
The following detailed description of the present invention will be made with reference to the accompanying drawings.
The invention provides a relay protection setting method for inverse time limit overload and a corresponding mathematical model, wherein the setting method comprises the following steps:
1. parameter relation of electrical quantity of basic data
Determining the rated capacity S of a ferroalloy furnace transformern(or rated current I)n) And allowing a long-time overload factor A, and the rated primary voltage U of the transformern。
(1) The relationship between transformer capacity, current and voltage is shown in equation 4,
Figure BDA0002189302950000031
the symbols in the formula are as follows:
In-transformingThe device is rated with primary current;
Sn-rated capacity of the transformer;
Un-rated primary voltage of the transformer.
(2) The long-time overload current allowed by the transformer is shown in equation 5,
Igh＝AIn (5)
the symbols in the formula are as follows:
Igh-long overload currents allowed by the transformer;
In-rated primary current of the transformer;
a-long time overload multiple allowed by the transformer.
(3) Determination of the overload factor A in the absence of relevant overload data
When the capacity of the iron alloy furnace transformer is not more than 33000kVA, the overload multiple A can be 1.3. When the capacity of the transformer of the iron alloy furnace is larger than 37000kVA, the overload multiple A can be 1.15.
The power supply system of the ferroalloy electric furnace is shown in figures 5-6.
2. Relay protection setting method
The action current of the protection device (to ensure non-action in case of long-time overload)
(1) When the capacity of the ferroalloy furnace is not more than 33000kVA, the action current accords with the formula 1 as follows:
Figure BDA0002189302950000041
the ferroalloy electric furnace 33MVA and the following general characteristic equation curve are shown in FIG. 1, and the action characteristic equation curve is shown in FIG. 3.
(2) When the variable capacity of the iron alloy furnace is more than 37000kVA, the action current accords with the formula 2 as follows:
Figure BDA0002189302950000042
the general characteristic equation curve of 37MVA of the ferroalloy electric furnace and the above is shown in figure 2, and the action characteristic equation curve is shown in figure 4.
(3) When the iron alloy electric furnace transformer is manufactured with special requirements, namely the allowable overload capacity of the transformer is not 1.3 times or 1.05 times of that of the formula 1 and the formula 2, but other values A, the mathematical curve model is as follows:
Figure BDA0002189302950000043
in the formula:
t-action time of protection;
Iop.k-an action current of the protection device;
In-the iron alloy furnace becomes the rated current of the high-pressure side;
a-the transformer allows long-time overload multiples;
the value of τ was calculated by substituting the data in Table 2 below into equation 3.
TABLE 2 setting calculation of iron alloy furnace transformers
Multiple of overload Iop.k/In 1.4 1.5 1.6 2 3 4 8
Corresponding time(s) 10～15 4～8 3～5 1～3 0.5～1 0.2～0.5 0～0.2
[ examples ] A method for producing a compound
The Ferro-iron alloy Limited liability company Toyobo first-stage 100-ten-thousand-ton ferroalloy project, wherein four and five workshops newly-installed ferroalloy ore-smelting electric furnaces have four seats, wherein the four workshop furnaces have the variable capacity of 33000kVA, the five workshop furnaces have the variable capacity of 37500kVA, and the rated primary voltage of the 16500kVA furnace is 110 kV.
In this embodiment, the improved calculation method provided by the present invention mainly solves the following key technical problems:
1. 31500kVA overload inverse time limit protection setting method for ferroalloy electric furnace transformer
According to equation 1, the setting of the load protection at this time should conform to the following equation:
Figure BDA0002189302950000051
the symbols in the formula are the same as those in formula 1.
Table 3 action characteristic verification
Figure BDA0002189302950000052
After one-time successful on-site heat load test, the running characteristic of the ferroalloy electric arc furnace conforms to the running rule of a 'general inverse time limit' characteristic curve.
Relay protection settingWhen the overload protection is carried out, a general inverse time-lag characteristic curve is selected, a curve formula accords with a formula 1, a setting value is shown in a table 3, and an initial value is set to be 1.3InSo that the protection device is activated above the current and deactivated below the current, with selectivity. When the rated current is 6-8 times, the protection action time is only 0.19-0.3 s, the current at the moment is generally considered as short-circuit fault current, and the traditional overload for the fault cannot be protected.
2. 37500kVA overload inverse time-limit protection setting method for iron alloy electric furnace transformer
According to equation 2, the setting of the load protection at this time should conform to the following equation:
Figure BDA0002189302950000061
the symbols in the formula are the same as those in formula 2.
Table 4 action characteristic verification
Figure BDA0002189302950000062
3. 16500kVA overload inverse time-limit protection setting method for ferroalloy electric furnace transformer
According to equation 3, the value of a for the overload protection of the electric furnace is generally 1.3, and the value of τ is calculated according to table 2 as follows:
Figure BDA0002189302950000063
therefore, τ is 0.0096-0.0144, and is taken as 0.01. The protective properties should therefore comply with the following formula:
Figure BDA0002189302950000071
the symbols in the formula are the same as those in formula 2.
Table 5 action characteristic verification
Figure BDA0002189302950000072
After one-time successful on-site heat load test, the running characteristic of the ferroalloy electric arc furnace conforms to the running rule of a 'general inverse time limit' characteristic curve.
Setting the relay protection, selecting a general inverse time-lag characteristic curve for overload protection, wherein the curve formula conforms to the formula 2, the setting value is shown in the table 4, and the starting value is set to be 1.05InSo that the protection device is activated above the current and deactivated below the current, with selectivity. When the rated current is 6-8 times, the protection action time is only 0.2-0.3 s, the current at the moment is generally considered as short-circuit fault current, and the traditional overload for the fault cannot be protected.
The above embodiments are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of the present invention is not limited to the above embodiments. The methods used in the above examples are conventional methods unless otherwise specified.

Claims (1)

1. An inverse time limit relay protection setting method of a ferroalloy furnace transformer is suitable for overload protection setting of the ferroalloy furnace transformer and similar electric arc furnace transformers, and is characterized in that:
when the capacity of the iron alloy electric furnace transformer is not more than 33000kVA, the mathematical curve model is as follows:
Figure FDA0003178056330000011
the Start value is set to 1.3InSo that the protection device is activated above this current and not activated below this current;
when the capacity of the iron alloy electric furnace transformer is larger than 37000kVA, the mathematical curve model is as follows:
Figure FDA0003178056330000012
the Start value is set to 1.05InSo that the protection device is activated above this current and not activated below this current;
when the iron alloy electric furnace transformer is manufactured with special requirements, namely the allowable overload capacity of the transformer is not 1.3 times or 1.05 times of that of the formula 1 and the formula 2, but other values A, the mathematical curve model is as follows:
Figure FDA0003178056330000013
in the formula:
t-action time of protection;
Iop.k-an action current of the protection device;
In-the iron alloy furnace becomes the rated current of the high-pressure side;
a-the transformer allows long-time overload multiples;
the value of tau is calculated by substituting the data in the following table into formula 3,
multiple of overload Iop.k/In 1.4 1.5 1.6 2 3 4 8 Corresponding time(s) 10～15 4～8 3～5 1～3 0.5～1 0.2～0.5 0～0.2
。
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105743073B (en) * 2016-04-13 2018-03-20 河海大学 A kind of inverse time over-current protection method
CN109617019A (en) * 2019-01-18 2019-04-12 日照南瑞电气科技有限公司 A kind of flame-proof mine double loop fan protection device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105743073B (en) * 2016-04-13 2018-03-20 河海大学 A kind of inverse time over-current protection method
CN109617019A (en) * 2019-01-18 2019-04-12 日照南瑞电气科技有限公司 A kind of flame-proof mine double loop fan protection device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
山区铁路牵引变压器反时限过负荷保护的应用研究;曲江浩;《电力学报》;20131031;第28卷(第5期);第374-377页 *

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