CN110556784A - relay protection configuration and setting method for high-voltage distribution system of ferroalloy electric furnace - Google Patents

relay protection configuration and setting method for high-voltage distribution system of ferroalloy electric furnace Download PDF

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Publication number
CN110556784A
CN110556784A CN201910952700.3A CN201910952700A CN110556784A CN 110556784 A CN110556784 A CN 110556784A CN 201910952700 A CN201910952700 A CN 201910952700A CN 110556784 A CN110556784 A CN 110556784A
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protection
current
transformer
overload
voltage
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CN110556784B (en
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郑伟
冯占立
杨冶
王罡世
李鹏
富钢
巴月娥
高贵军
耿全德
李子良
殷业鹏
于雷
陈鹏超
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Ansteel Engineering Technology Corp Ltd
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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
    • H02H3/02—Details
    • H02H3/05—Details with means for increasing reliability, e.g. redundancy arrangements
    • 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
    • H02H3/08—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 responsive to excess current
    • 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
    • H02H3/08—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 responsive to excess current
    • H02H3/10—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 responsive to excess current additionally responsive to some other abnormal electrical conditions
    • H02H3/105—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 responsive to excess current additionally responsive to some other abnormal electrical conditions responsive to excess current and fault current to earth
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Protection Of Transformers (AREA)

Abstract

A method for configuring and setting the relay protection of a high-voltage distribution system of an iron alloy electric furnace comprises overload protection, instantaneous current quick-break protection and low-voltage blocking overcurrent protection; the instantaneous current quick-break protection is used as main protection and is set to be effective when a short-circuit fault occurs in the transformer; the low-voltage lockout overcurrent protection is used as backup protection of instantaneous quick-break protection and is effective when the low-current ground fault of the transformer occurs; the inverse time limit overload protection has inverse time limit characteristics, is used as backup protection of instantaneous quick-break protection and low-voltage lockout overcurrent protection, is 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; each protection can be used as a backup for the latter protection, especially in high-side, non-grounded systems or in places far from the power system where the neutral point is the high-voltage side, although the fault current is small, the low-voltage blocking overcurrent and the inverse-time overload protection used can be effective.

Description

relay protection configuration and setting method for high-voltage distribution system of ferroalloy electric furnace
Technical Field
The invention relates to the technical field of energy generation, power supply and power distribution, in particular to a relay protection configuration and setting method for a high-voltage power distribution system of an iron alloy electric 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
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.
the existing setting of microcomputer relay protection before the operation of the ferroalloy electric furnace has no relevant regulations of national unified standards and regulation specifications, so that the configuration scheme and setting of the relay protection are stopped on the traditional relay scheme, the protection scheme is too simple, only two schemes of 'quick-break' and 'timing limit' protection are provided, the operation of modern large-scale submerged arc furnace equipment cannot be met, and particularly in places with a neutral point ungrounded system on a high-voltage side or far away from a power system, the fault current is small, the operation requirements cannot be met according to the configuration setting method in the table 1, and the fault cannot be removed quickly.
disclosure of Invention
in order to solve the technical problems in the background art, the invention provides a relay protection configuration and setting method for a high-voltage distribution system of a ferroalloy electric furnace, and three protection schemes and setting methods of the invention are in ring-to-ring buckling on a protection range, each protection can be used as backup protection of the latter protection, particularly in a place with a neutral point on a high-voltage side being a non-grounded system or far away from an electric power system, although fault current is small, the used low-voltage blocking overcurrent and inverse time-limit overload protection can be effective.
In order to achieve the purpose, the invention adopts the following technical scheme:
A method for configuring the relay protection of a high-voltage distribution system of an iron alloy electric furnace comprises overload protection, instantaneous current quick-break protection and low-voltage lockout overcurrent protection;
1) The instantaneous current quick-break protection is used as main protection and is set to be effective when a short-circuit fault occurs in the transformer;
2) the low-voltage lockout overcurrent protection is used as backup protection of instantaneous quick-break protection and is effective when the low-current ground fault of the transformer occurs;
3) The inverse time limit overload protection has inverse time limit characteristics, is used as backup protection of instantaneous quick-break protection and low-voltage lockout overcurrent protection, is 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; in the event of a fault, the larger the fault current, the shorter the operation time.
the setting method of the instantaneous current quick-break protection comprises the following steps: operating current Idzjthe switching-on excitation surge current when the transformer is put into operation is avoided, and the following calculation formula is adopted:
the sensitivity of the protection installation is not less than 2 when two-phase short-circuit current occurs in the minimum operation mode;
kjxThe connection coefficient, when connected to the phase current, is 1.0, and when connected to the line current, is √ 3;
Ied-rated current of the transformer;
ki-current transformer transformation ratio;
Ksen-sensitivity;
I"dmin2-two phase short circuit current value in minimum operation mode;
8-12-a large-capacity electric furnace, taking 8.0; and taking 12.0 parts of a small-capacity electric furnace.
The setting method of the low-voltage latch comprises the following steps:
operating current Idzjrated current and action voltage U avoiding transformerdzjThe lowest working voltage which is possibly generated when the transformer normally operates is avoided, and when the two conditions are met, the protection action is calculated according to the following formula:
Udzj＝(0.5～0.7)Un
when the two conditions are simultaneously met, the fault working state of the submerged arc furnace is judged;
The sensitivity of the protection installation is not less than 1.5 when two-phase short-circuit current occurs in the minimum operation mode;
the action current of the protection device is ensured not to act under the condition of allowing long-time overload;
Udzj-an actuation voltage of the protection device;
KrThe return coefficient of the microcomputer protection device is 0.9-0.95;
Un-rated voltage of the transformer.
the setting method of the inverse time limit overload protection comprises the following steps:
(1) when the capacity of the iron alloy electric furnace transformer is not more than 33000kVA, the allowable overload capacity of the transformer is 1.3 times, and the inverse time limit overload protection mathematical curve model is as follows:
(2) when the capacity of the iron alloy electric furnace transformer is larger than 37000kVA, the allowable overload capacity of the transformer is 1.05 times, and the inverse time-limit overload protection mathematical curve model is as follows:
(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 inverse time overload protection mathematical curve model is as follows:
TABLE 3 setting calculation of iron alloy furnace transformers
multiple of overload I/Ied 1.4 1.5 1.6 2 3 4 8
Corresponding time tau(s) 10～15 4～8 3～5 1～3 0.5～1 0.2～0.5 0～0.2
In the formula:
The value of tau is calculated by substituting the data in the table into formula 3;
t-action time of protection;
I, protecting the action current;
Ied-ferroalloy furnace transformer current rating;
a-the transformer allows long overload times.
Compared with the prior art, the invention has the beneficial effects that:
1. the method fills the blank in the industry, and the relay protection of a microcomputer is not set before the operation of the current ferroalloy electric furnace, and has no relevant regulations of national unified standards and regulation specifications, so that the configuration scheme and the setting of the relay protection are stopped on the traditional relay scheme, the protection scheme is too simple, only two schemes of 'quick break' and 'timing limit' protection are provided, the operation of modern large-scale submerged arc furnace equipment cannot be met, particularly in a place with a neutral point on a high-voltage side of a non-grounded system or far away from an electric power system, the traditional configuration and setting scheme cannot effectively cut off faults due to small fault current, and the low-voltage blocking overcurrent and inverse time limit overload protection used by the method can be effective. The three protection schemes and the setting method are in ring buckling on the protection range, and each protection can be used as a backup protection of the latter protection. The invention discloses a protection device, which can randomly select a long-delay inverse time limit curve (3 times of action current, 6s) and the like, summarizes a typical relay protection mathematical model of a transformer of a ferroalloy furnace through multiple times of debugging after the field actual operation, and finds that the ferroalloy furnace belongs to the general inverse time limit operation characteristic in the power field.
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 is a 110kV power supply system of an iron alloy electric furnace FIG. 2(37500 kVA);
fig. 7 is a schematic diagram of the relay protection range of the ferroalloy electric furnace.
In the figure: 1-quick-break protection range (with dead zone, capable of extending to a part of an electric furnace), 2-low voltage lockout overcurrent protection range (without dead zone, quick-break near backup protection) 3-inverse time-limit overload protection (without dead zone, low voltage lockout backup protection).
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 configuration scheme and an inverse time limit overload relay protection mathematical model, wherein the relay protection scheme is shown in a table 2, and the relay protection configuration and setting method of a high-voltage distribution system of a ferroalloy electric furnace is organized as follows:
TABLE 2 Relay protection configuration and setting calculation for iron alloy furnace transformers
As shown in fig. 5-7:
1) The current quick-break protection is used as main protection, and is mainly designed for short-circuit faults inside a transformer, and three-phase and two-phase short-circuit faults are impossible to occur inside the transformer (three single-phase transformers are arranged in a delta shape) due to the structural type of the iron alloy furnace transformer, but two-phase short-circuit faults are possible, so the quick-break protection plays a role in protecting when single-phase grounding and two-phase short-circuit faults occur, and equipment damage is avoided to the maximum extent.
2) the low-voltage lockout overcurrent protection is mainly used as backup protection of 'quick-break protection', the characteristics of low voltage and large current unique to short-circuit fault can be identified, the setting current is only rated current of the transformer, the sensitivity of relay protection is greatly improved, the low-voltage lockout overcurrent protection has a good protection effect on the low-current ground fault of the transformer, and meanwhile, the low-voltage characteristic can ensure normal operation of equipment.
3) the inverse time limit overload protection is that the model curve has inverse time limit characteristics, can be matched with an operation curve of the ferroalloy electric furnace transformer 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 backup protection has better selectivity and rapidity, and can be used as the backup protection of 'quick-break protection' and 'low-voltage lockout overcurrent protection'.
The specific setting principle and method are as follows:
1. Parameter relation of electrical quantity of basic data
determining the rated capacity S of a ferroalloy furnace transformern(or rated current I)ed) 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:
the symbols in the formula are as follows:
Ied-rated current of the transformer;
Sn-rated capacity of the transformer;
Un-rated voltage of the transformer.
(2) The long-time overload current allowed by the transformer is shown in formula 5:
Igh＝AIed (5)
The symbols in the formula are as follows:
Igh-long overload currents allowed by the transformer;
Ied-rated 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.
2. Relay protection setting
(1) Quick-break protection:
The action value avoids the switching-on excitation inrush current when the transformer is put into use, and the formula is shown as formula 6:
The sensitivity of the protective installation should be no less than 2 in the event of a two-phase short-circuit current in the minimum operating mode.
the symbols in the formula are as follows:
Igh-long overload currents allowed by the transformer;
Ied-rated current of the transformer;
a is the long-time overload multiple allowed by the transformer;
Ksensensitivity (ratio of short circuit current to setting current).
(2) Low voltage lockout over-current protection:
When the action value avoids the rated current of the transformer and the voltage avoids the lowest working voltage which may appear when the transformer normally operates, the action is protected, see formula 8:
Udzj＝(0.5～0.7)Un (9)
when the two conditions are simultaneously met, the fault working state of the submerged arc furnace is judged.
The sensitivity of the protective installation should be no less than 1.5 at the minimum operating mode in the presence of two-phase short-circuit currents.
the action current of the protection device (which should be guaranteed not to act in case of allowing long-time overload);
Udzj-an actuation voltage of the protection device;
Krthe return coefficient of the microcomputer protection device is generally 0.9-0.95;
Other symbols are illustrated in equations 6 and 7.
(3) Overload protection (inverse time limit):
The action current of the protection device (to ensure non-action in case of long-time overload)
1) when the capacity of the iron alloy electric furnace transformer is not more than 33000kVA, the allowable overload capacity of the transformer is 1.3 times, and the inverse time limit overload protection mathematical curve model is as follows:
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 capacity of the iron alloy electric furnace transformer is larger than 37000kVA, the allowable overload capacity of the transformer is 1.05 times, and the inverse time-limit overload protection mathematical curve model is as follows:
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 inverse time overload protection mathematical curve model is as follows:
TABLE 3 setting calculation of iron alloy furnace transformers
multiple of overload I/Ied 1.4 1.5 1.6 2 3 4 8
corresponding time tau(s) 10～15 4～8 3～5 1～3 0.5～1 0.2～0.5 0～0.2
In the formula:
The value of tau is calculated by substituting the data in the table into formula 3;
t-action time of protection;
I, protecting the action current;
Ied-ferroalloy furnace transformer current rating;
A-the transformer allows long overload times.
[ examples ] A method for producing a compound
The Ferro-ferroalloy Limited liability company Toyobo first-stage 100-ten-thousand-ton ferroalloy engineering is characterized in that four and five workshops of new ferroalloy ore-smelting electric furnaces share four seats, wherein the four workshop furnaces have the capacity of 33000kVA, the five workshop furnaces have the capacity of 37500kVA, the rated primary voltage of 16500kVA furnace transformer is 110kV, and the 110kV side protects short-circuit current I at installation position "dmin2about 10kA, short-circuit current I at the outlet of the low-pressure side of the furnace "dLmin2not exceeding 3 times of rated current of the transformer.
in this embodiment, the improved calculation method provided by the present invention mainly solves the following key technical problems:
1. 33000kVA quick-break protection setting of iron alloy electric furnace transformer
and (5) obtaining 27A.
Protection action time limit: 0 s.
and (3) sensitivity checking:
2. 33000kVA low-voltage blocking iron overcurrent protection setting device of iron alloy electric furnace transformer
and 5.5A is taken out.
Udzj＝(0.5～0.7)UnThe actual value is 55V, which is 50V to 70V.
Protection action time limit: 0.2 s.
When the two conditions are simultaneously met, the fault working state of the submerged arc furnace is judged.
According to the setting result, when the relay protection has a fault corresponding to the 'quick-break' protection, the low-voltage lockout overcurrent protection is started, and the time is 0.2s later than the quick-break, so that the reliability (backup protection of the quick-break protection) is increased while the protection selectivity is ensured.
and (3) sensitivity checking:
3. 33000kVA inverse time limit overload protection setting of ferroalloy electric furnace transformer
According to equation 1, the setting of the load protection at this time should conform to the following equation:
table 4 action characteristic verification
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 time of relay protection, selecting general inverse time-limit characteristic curve for overload protection, and making the curve formula conform to the publicformula 1, setting value shown in Table 3, and initial value set to 1.3IedSo 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.
4. 37500kVA quick-break protection setting of ferroalloy electric furnace transformer
And (5) taking 31A.
protection action time limit: 0 s.
and (3) sensitivity checking:
5. 37500kVA low-voltage blocking iron over-current protection setting device of iron alloy electric furnace transformer
the extract was 6.5A.
Udzj＝(0.5～0.7)UnThe actual value is 55V, which is 50V to 70V.
Protection action time limit: 0.2 s.
When the two conditions are simultaneously met, the fault working state of the submerged arc furnace is judged.
according to the setting result, when the relay protection has a fault corresponding to the 'quick-break' protection, the low-voltage lockout overcurrent protection is started, and the time is 0.2s later than the quick-break, so that the reliability (backup protection of the quick-break protection) is increased while the protection selectivity is ensured.
And (3) sensitivity checking:
6. 37500kVA inverse time limit overload protection setting device of ferroalloy electric furnace transformer
according to equation 2, the setting of the load protection at this time should conform to the following equation:
table 5 action characteristic verification
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 1.05Iedso 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.
7. 16500kVA quick-break protection setting of iron alloy electric furnace transformer
And (5) taking 15A.
protection action time limit: 0 s.
and (3) sensitivity checking:
8. 16500kVA low-voltage blocking iron over-current protection setting of iron alloy electric furnace transformer
2.5A.
Udzj＝(0.5～0.7)Unthe actual value is 55V, which is 50V to 70V.
Protection action time limit: 0.2 s.
When the two conditions are simultaneously met, the fault working state of the submerged arc furnace is judged.
According to the setting result, when the relay protection has a fault corresponding to the 'quick-break' protection, the low-voltage lockout overcurrent protection is started, and the time is 0.2s later than the quick-break, so that the reliability (backup protection of the quick-break protection) is increased while the protection selectivity is ensured.
and (3) sensitivity checking:
9. 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 1.2, and the value of τ is calculated according to Table 2 as follows:
therefore, τ is 0.002-0.031, and 0.0025 is selected. The protective properties should therefore comply with the following formula:
the symbols in the formula are the same as those in formula 2.
Table 6 action characteristics verification
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 1.2Iedso 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 0.35-0.5 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 (4)

1. a method for configuring the relay protection of a high-voltage distribution system of an iron alloy electric furnace is characterized by comprising overload protection, instantaneous current quick-break protection and low-voltage lockout overcurrent protection;
1) the instantaneous current quick-break protection is used as main protection and is set to be effective when a short-circuit fault occurs in the transformer;
2) The low-voltage lockout overcurrent protection is used as backup protection of instantaneous quick-break protection and is effective when the low-current ground fault of the transformer occurs;
3) the inverse time limit overload protection has inverse time limit characteristics, is used as backup protection of instantaneous quick-break protection and low-voltage lockout overcurrent protection, is 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; in the event of a fault, the larger the fault current, the shorter the operation time.
2. the method for configuring the relay protection of the high-voltage distribution system of the ferroalloy electric furnace according to claim 1, wherein the setting method of the instantaneous current quick-break protection comprises the following steps: operating current IdzjThe switching-on excitation surge current when the transformer is put into operation is avoided, and the following calculation formula is adopted:
The sensitivity of the protection installation is not less than 2 when two-phase short-circuit current occurs in the minimum operation mode;
kjxthe connection coefficient, when connected to the phase current, is 1.0, and when connected to the line current, is √ 3;
Ied-rated current of the transformer;
ki-current transformer transformation ratio;
Ksen-sensitivity;
I"dmin2-two phase short circuit current value in minimum operation mode;
8-12-a large-capacity electric furnace, taking 8.0; and taking 12.0 parts of a small-capacity electric furnace.
3. the method for configuring the relay protection of the high-voltage distribution system of the ferroalloy electric furnace according to claim 1, wherein the method for setting the low-voltage latch comprises the following steps:
operating current IdzjRated current and action voltage U avoiding transformerdzjThe lowest working voltage which is possibly generated when the transformer normally operates is avoided, and when the two conditions are met, the protection action is calculated according to the following formula:
Udzj＝(0.5～0.7)Un
when the two conditions are simultaneously met, the fault working state of the submerged arc furnace is judged;
the sensitivity of the protection installation is not less than 1.5 when two-phase short-circuit current occurs in the minimum operation mode;
The action current of the protection device is ensured not to act under the condition of allowing long-time overload;
Udzj-an actuation voltage of the protection device;
KrThe return coefficient of the microcomputer protection device is 0.9-0.95;
Un-rated voltage of the transformer.
4. the method for configuring the relay protection of the high-voltage distribution system of the ferroalloy electric furnace according to claim 1, wherein the method for setting the inverse time-limit overload protection comprises the following steps:
(1) When the capacity of the iron alloy electric furnace transformer is not more than 33000kVA, the allowable overload capacity of the transformer is 1.3 times, and the inverse time limit overload protection mathematical curve model is as follows:
(2) When the capacity of the iron alloy electric furnace transformer is larger than 37000kVA, the allowable overload capacity of the transformer is 1.05 times, and the inverse time-limit overload protection mathematical curve model is as follows:
(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 inverse time overload protection mathematical curve model is as follows:
Multiple of overload I/Ied 1.4 1.5 1.6 2 3 4 8 Corresponding time tau(s) 10～15 4～8 3～5 1～3 0.5～1 0.2～0.5 0～0.2
In the formula:
The value of tau is calculated by substituting the data in the table into formula 3;
t-action time of protection;
i, protecting the action current;
Ied-ferroalloy furnace transformer current rating;
A-the transformer allows long overload times.
CN201910952700.3A 2019-10-09 2019-10-09 Relay protection configuration and setting method for high-voltage distribution system of ferroalloy electric furnace Active CN110556784B (en)

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