CN102288316A - Digital transformer winding temperature measuring device - Google Patents

Abstract

The invention discloses a digital transformer winding temperature measuring device, comprising a current converter, a relation computation module, a thermal simulation computation module, a response time setting module and an addition computation module as well as an oil temperature sensor and a temperature display and control module. The current converter is connected with the relation computation module; the relation computation module is connected with a thermal simulation computation module; the thermal simulation computation module, the oil temperature sensor and the temperature display and control module are connected with the addition computation module, respectively; and the response time setting module is connected with the thermal simulation computation module. In the invention, the current converter and a circuit module are added, so that outputting of a current signal is realized, a microprocessor is used for calculating transformer winding temperature by means of mathematic modelling, and the effects of high accuracy, high automation and use convenience are achieved.

Description

Digital transformer winding temperature measurement mechanism

Technical field

The present invention relates to a kind of temperature measuring equipment, particularly a kind of digital temperature measurement mechanism that is applicable to Transformer Winding.

Background technology

The thermal characteristics of Transformer Winding has determined the load capacity and the insulation probable life thereof of power transformer, and this makes the deciding factor that the Transformer Winding temperature becomes influences the power transformer operate as normal.Therefore in time grasp the winding temperature of transformer, significant to safety, the economical operation of guaranteeing transformer.The measuring transformer winding temperature mainly is to adopt mechanical type Transformer Winding temperature measuring equipment at present, measure the Transformer Winding temperature approx by the thermal simulation principle, but be subjected to the structural limitations of traditional mechanical pointer instrument, not only measuring accuracy is low for this mechanical type temperature measuring equipment, need often calibration, can't accurately reflect winding temperature; And volume is bigger than normal, and inconvenience is installed, and automaticity is low, is not easy to operation, influences work efficiency.

Summary of the invention

The present invention mainly solves existing Transformer Winding temperature measuring equipment and is subjected to structural limitations can't accurately measure winding temperature, automaticity is low, be not easy to technical matterss such as operation, a kind of measuring accuracy height, automaticity height, Transformer Winding temperature measuring equipment easy to install are provided.

Above-mentioned technical matters of the present invention is mainly solved by following technical proposals:

The present invention includes and be used for the output current current transformer of measuring transformer indirectly; Be used for the average temperature rising that winding reaches after the thermal equilibrium and concern computing module; Be used to calculate the thermal simulation computing module of Current Temperatures side-play amount; Be used to set the response time setting module of thermal response time; Be used to calculate the additional calculation module of winding temperature; The oil temperature sensor that is used for the top-oil temperature of measuring transformer; And the temperature that is used to export result of calculation and realize relevant control shows and control module;

It is characterized in that: current transformer links to each other with concerning computing module, concerns that computing module links to each other with the thermal simulation computing module, and thermal simulation computing module, oil temperature sensor and temperature show and link to each other with the additional calculation module respectively with control module; The response time setting module connects the thermal simulation computing module.

Further, the computing formula that concerns computing module is: Δ T=a ₀+ a ₁* I _t+ a ₂* I _t ², wherein: a ₀=-0.592166414611468,

a ₁＝1.92532306426727E-03，

a ₂＝1.72397453373464E-05。

Further, the difference equation of thermal simulation computing module is:

Y(n)＝aΔT(n)+(1-a)Y(n-1)

Wherein, Δ T (n) is the current pairing stable state average temperature rising of transformer output current, and Y (n) is current temperature offset amount; Temperature offset amount when Y (n-1) is last the sampling; A is the relevant parameter of setting with the response time setting module of response time.

Further, the additional calculation module is according to formula: T _r=T ₀+ Y (n) calculates the Transformer Winding temperature.

The invention has the beneficial effects as follows: by the Transformer Winding Temperature Rise characteristic is carried out mathematical modeling, utilize the method for computed in software to reach the purpose of thermal simulation, make full use of microprocessor technology, improve problems such as big, the difficult operation of original Transformer Winding thermometry error, reach the effect of reliability height, automaticity height, operation and maintenance convenience, long service life.

Description of drawings

Accompanying drawing 1 is the principle of work block diagram of digital transformer winding temperature measurement mechanism;

Accompanying drawing 2 well heater typical temperature increase curves;

Accompanying drawing 3 thermal simulation characteristic-temperature rises and electric current corresponding tables;

The step response curve of accompanying drawing 4 first-order systems;

The software flow pattern of accompanying drawing 5 Transformer Winding temperature surveys, calculating.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is done further specific description.

As shown in Figure 1, digital transformer winding temperature measurement mechanism is to utilize mathematical modeling to realize the thermal simulation effect.Current transformer 1 links to each other with transformer, is used for the output current of measuring transformer indirectly.Electric current to current transformer 1 output is measured, and obtains a watt current value that is directly proportional with transformer load, and offers and concern computing module 2.Concern that computing module 2 calculates realization by microprocessor software, according to the electric current of current transformer 1 output and the corresponding relation of temperature rise, when calculating transformer was exported certain current value, winding reached the average temperature rising after the thermal equilibrium.Thermal simulation computing module 3 is calculated by microprocessor software equally and finishes, and according to the temperature characteristic of transformer, the thermal response time constant according to concerning that computing module 2 resulting current transformer average temperature risings and user set calculates current temperature offset amount.Oil temperature sensor 4 adopts thermistor, as the thermal resistance PT100 of armouring, is used for the top-oil temperature of measuring transformer.5 pairs of above-mentioned gained data of additional calculation module are carried out integration processing, calculate winding temperature.Response time setting module 6 is used to set thermal response time.Temperature shows with control module 7 and is used to export result of calculation and realizes relevant control, as cooling, tripping operation control etc.

Further, current transformer 1 links to each other with concerning computing module 2, concerns that computing module 2 links to each other with thermal simulation computing module 3, and thermal simulation computing module 3, oil temperature sensor 4 and temperature show and link to each other with additional calculation module 5 respectively with control module 7; Response time setting module 6 connects thermal simulation computing module 3.

Referring to accompanying drawing 1, the principle of work of digital transformer winding temperature measurement mechanism of the present invention is:

By the measuring transformer reservoir temperature, the temperature offset amount relevant with the transformer output current that superposes is as the average temperature value of Transformer Winding.Utilization thermal simulation principle, promptly according to the regulation of IEC354 " transformer load guide rule ", oil-immersed power transformer winding temperature T _rCan equivalence be:

T _r＝T ₀+K _i? _ΔT

Be that hot spot temperature of winding is additional temperature rise _ΔT and top-oil temperature T ₀Function.In the formula _ΔT is the additional temperature rise that thermal cycle simulation provides, K _iBe the focus coefficient relevant with transformer device structure.T in the formula ₀Can use oil temperature sensor 4 to obtain, its principle is to utilize the variation of thermistor induction top-oil temperature, and this technology is very ripe, can realize with the thermal resistance PT100 of armouring.In other words, if can record the additional temperature rise that thermal cycle simulation provides _ΔT also just can draw hot spot temperature of winding T _r

When on the transformer belt during load,, in actual applications, generally come the output current of indirect measuring transformer by current transformer because the output current of transformer is excessive.Behind load on the transformer belt, the electric current that is directly proportional with its load is through current transformer 1 conversion, to concerning that computing module 2 provides a current signal I _t

The principle of work that concerns computing module 2 is: referring to accompanying drawing 3, and during for the extra current of regulation current transformer output 0.5A～5A among the national sector standard JB/T8450-2005, the corresponding form of the additional temperature rise that thermal cycle simulation produced.According to this temperature rise and electric current corresponding tables, can determine the average temperature rising Δ T that thermal cycle simulation produces.By least square method, can simulate additional temperature rise Δ T and current transformer output current I _tMathematic(al) representation, be the operational formula that concerns computing module 2:

ΔT＝a ₀+a ₁×I _t+a ₂×I _t ²

Wherein: a0=-0.592166414611468,

a1＝1.92532306426727E-03，

a2＝1.72397453373464E-05。

By the response time and the sampling period of response time setting module 6 setting thermal simulations, calculate the temperature offset amount of thermal simulation system by thermal simulation computing module 3.

The principle of work of thermal simulation computing module 3 is: by the mathematical modeling mode, according to the first-order system principle, with the electric current I of transformer _h, parameter such as average temperature rising Δ T and time relation carry out mathematical modeling, calculates current winding additional temp side-play amount by microprocessor.Referring to accompanying drawing 2 are typical well heater temperature rise curves when adding the electric current of fixed size.Analyze this curve, can find that itself and first-order system have approximate characteristic.Promptly adopt the first-order lag responding system to describe the well heater model of analogue transformer heating in winding among the present invention.The transport function in first-order system S territory is:

$H\left(S\right)=\frac{1}{\mathrm{TS}+1}$

If n is a systematic sampling time number variable, then the difference equation of thermal simulation computing module 3 is:

Y(n)＝a?X(n)+(1-a)Y(n-1)

Wherein, X (n) is the current pairing stable state average temperature rising of transformer output current, i.e. Δ T value during the n time sampling, and Y (n) is current temperature offset amount; Temperature offset amount when Y (n-1) is last the sampling.

In above-mentioned formula, a is the relevant parameter of setting with response time setting module 6 of response time, and the time constant of establishing first-order system is τ, and the sampling period is Ts, according to the first-order system function, then has:

$a=\frac{\mathrm{Ts}}{\mathrm{Ts}+\mathrm{\τ}}$

Referring to the step response curve of accompanying drawing 4 first-order systems as can be known, when time t was 4 τ, output valve was 98.2% of a steady-state value, can be similar to as the steady-state response value; If the temperature rise response time of first-order system is Γ, Γ=4 τ are arranged then; Owing to require the thermal simulation time constant to be not more than 9min among the national sector standard JB/T 8450-2005, i.e. 540s is so have Γ≤540s, τ≤135s.

Further, establishing sampling rate is Fs, and the closed-loop bandwidth of single order responding system is F _BW,, in actual applications, select sampling rate greater than 20 times closed-loop bandwidth F then according to the practical experience of technology and cost _BWComparatively reasonable, i.e. Fs＞20F _BWBecause Ts=1/Fs, so have:

$\mathrm{Ts}<\frac{1}{20F_{\mathrm{BW}}}$

System for a rise time is Γ can get closed-loop bandwidth F _BWFor Promptly The reasonable value scope that therefore can get sampling period Ts is Ts＜0.4 τ, i.e. Ts＜54s; Take all factors into consideration the display refresh rates of measurement result and the factors such as reaction velocity of control output, generally Ts is decided to be 1s.

Behind response time control module 6 definite response time τ and sampling period Ts, can calculate the concrete numerical value of parameter a.

Because oil-immersed power transformer winding average temperature value is: transformer oil reservoir temperature, a temperature offset amount relevant with the transformer output current superposes.Utilize the additional calculation module, calculating transformer winding average temperature value, this computing formula is: T _r=T ₀+ Y (n).The numerical value that calculates gained is shown and control module 7 outputs by temperature, and is regulated and control.

Thermal simulation system among the present invention adopts microprocessor to realize.Concern computing module 2 and thermal simulation computing module 3 as shown in accompanying drawing 1 adopt microprocessor technology, and related data is carried out analyzing and processing.The software flow of winding temperature measurement, calculating section as shown in Figure 5.Utilize the present invention can reach adjusting, easy to use, the precision height does not need frequent calibration, the automaticity height, and the response time is adjustable, the little effect of drifting about.

Claims (4)

1. digital transformer winding temperature measurement mechanism comprises:

Be used for the output current current transformer of measuring transformer indirectly; Connect the computing module that concerns of current transformer, be used to calculate the average temperature rising after winding reaches thermal equilibrium; Be used to set the response time setting module of thermal response time; The oil temperature sensor that is used for the top-oil temperature of measuring transformer; And the temperature that is used to export result of calculation and realize relevant control shows and control module;

It is characterized in that: also comprise the thermal simulation computing module of annexation computing module and response time setting module, be used for the side-play amount of calculating transformer Current Temperatures; And the additional calculation module that connects thermal simulation computing module, oil temperature sensor and temperature demonstration and control module, the additional calculation module is used to calculate current transformer and goes out winding temperature.

2. digital transformer winding temperature measurement mechanism as claimed in claim 1 is characterized in that: the computing formula that concerns computing module is: Δ T=a ₀+ a ₁* I _t+ a ₂* I _t ²,

Wherein: a ₀=-0.592166414611468,

a ₁＝1.92532306426727E-03，

a ₂＝1.72397453373464E-05。

3. digital transformer winding temperature measurement mechanism as claimed in claim 1, it is characterized in that: the difference equation of thermal simulation computing module is:

Y(n)＝aΔT(n)+(1-a)Y(n-1)

Wherein, Δ T (n) is the current pairing stable state average temperature rising of transformer output current, and Y (n) is current temperature offset amount; Temperature offset amount when Y (n-1) is last the sampling; A is the relevant parameter of setting with the response time setting module of response time.

4. digital transformer winding temperature measurement mechanism as claimed in claim 1, it is characterized in that: the additional calculation module is according to formula: T _r=T ₀+ Y (n) calculates the Transformer Winding temperature.