Zorica Bogicevic 1 and Slobodan Bjelic 2 and Petar Spalevic 2 and Milan Misic 1
Academic Editor:Hou-Sheng Su
1, Higher Technical Professional School in Zvecan, Nusiceva 6, 38227 Zvecan, Serbia
2, Faculty of Technical Sciences, University of Pristina, Kneza Milosa 7, 38220 Kosovska Mitrovica, Serbia
Received 11 June 2015; Accepted 6 September 2015; 27 October 2015
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
In addition to classical methods, one of the possible methods for obtaining the values and parameters of the transformer is graph-analytical method based on the construction of phase diagrams for different types of transformer loads.
Three-phase two-coiled transformer (Figure 1(a)) has HV/LV coils in coupling [figure omitted; refer to PDF] (or [figure omitted; refer to PDF] ) [1]. In the delta or star coupling HV transformers' coils, phase voltages have a sinusoidal shape and the same form of voltage that has the network from which the transformer is supplied. In symmetrical regime, the analysis of three-phase transformers is reduced to the analysis of the schemes of equivalent single-phase transformers. Equivalent single-phase diagram gives a picture of the three-phase system only if the system in all three phases has equal impedances [figure omitted; refer to PDF] , through the same modules flow as the same voltage modules [figure omitted; refer to PDF] act on impedance. Single-phase transformer with two windings corresponds to equations where secondary values are reduced to the primary side (Figure 1(f)) [1]: [figure omitted; refer to PDF]
Figure 1: Measurement graph-analytical transformer model for (a) [figure omitted; refer to PDF] grope, (b) no-load, (c) short-circuit, (d) load, (e) high frequencies, (f) single load transformer, (g) and equivalent circuit of transformer.
(a) [figure omitted; refer to PDF] -grope
[figure omitted; refer to PDF]
(b) No-load
[figure omitted; refer to PDF]
(c) Short-circuit
[figure omitted; refer to PDF]
(d) Loads [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , [figure omitted; refer to PDF]
[figure omitted; refer to PDF]
(e) High frequencies
[figure omitted; refer to PDF]
(f) [figure omitted; refer to PDF]
(g) [figure omitted; refer to PDF]
The electrical circuit secondary values must be expressed in a way that the primary voltage refers to the primary current. At the beginning the current [figure omitted; refer to PDF] must be determined in relation to ems [figure omitted; refer to PDF] and to the parameters of the circuit: [figure omitted; refer to PDF] By replacing the previous dependencies into the voltage equation [figure omitted; refer to PDF] the following is obtained: [figure omitted; refer to PDF] From relation (4) it is clear that equivalent circuit of the transformer, where the primary current [figure omitted; refer to PDF] passes, must have equivalent impedance [figure omitted; refer to PDF] . This impedance is presented in the circuit and is described in Figure 1, where the series connection [figure omitted; refer to PDF] with the parallel combination [figure omitted; refer to PDF] and [figure omitted; refer to PDF] is shown and parameters of transformers, which are included with losses, are in classical-conventional manner measured in the experiment of idling (no-load) and in the short-circuit test. For small power transformers, due to difficulties in measuring active losses this method is practically not applicable.
A classic method (Section 2) and the proposed-analytical method (Section 3) are shown in this paper. The model proposed in this paper is verified by simulation in MATLAB Simulink software package (Section 4). In the adapted simulation model for three different ABB transformers of low power, tabular and graphical results are obtained (Section 5).
2. Measurement of Transformer's Impedance
2.1. The Short-Circuit Test
The equations of transformer when it is not loaded (Figure 1(b)), for defined primary impedance [figure omitted; refer to PDF] , can be formulated on the basis of the general system of [1, 2] [figure omitted; refer to PDF] If the impedance load is great ( [figure omitted; refer to PDF] ), the value of secondary current is equal to zero: [figure omitted; refer to PDF] The medium values of phase currents and medium voltage values are obtained by three-phase transformer in idling current: [figure omitted; refer to PDF] Based on the values [figure omitted; refer to PDF] [figure omitted; refer to PDF] [figure omitted; refer to PDF] [figure omitted; refer to PDF] researcher can determine idling power factor [figure omitted; refer to PDF] . The sizes of the transformer which can be determined from experiments of idling at rated voltage are as follows.
Transmission ratio of the transformer, which is the ratio of secondary and primary rated voltage at idle, is as follows: [figure omitted; refer to PDF] Idle current [figure omitted; refer to PDF] , idle current and its relative value, as a part of rated primary current in p.u. system, are as follows: [figure omitted; refer to PDF] The mutual impedance, defined when [figure omitted; refer to PDF] , is as follows: [figure omitted; refer to PDF] Its active component is obtained as [figure omitted; refer to PDF] and reactive component-reactance is obtained as [figure omitted; refer to PDF]
2.2. Losses in Idling
When the voltage is equal to the nominal [figure omitted; refer to PDF] practically do not differ from losses in the magnetic circuit (core), [figure omitted; refer to PDF] , because the losses at primer's copper, [figure omitted; refer to PDF] , in those conditions are small, since the current [figure omitted; refer to PDF] has low value. The magnetization characteristic of any magnetic circuit made by ferromagnetic material contains information about the useful flux saturation degree [3, 4]. In the paper magnetic has value of residual flux since there is no load (provided that it is [figure omitted; refer to PDF] predominantly unchanged) [5, 6]. However, at rated voltage, the losses in the core [figure omitted; refer to PDF] are about the same as losses at idle, [figure omitted; refer to PDF] , that is, total idle losses: [figure omitted; refer to PDF] , [figure omitted; refer to PDF] . Dangerous transient currents of the transformer can occur if a short-circuit on the secondary side happened at rated voltage [figure omitted; refer to PDF] [7].
2.3. The Short-Circuit Test
Secondary side of transformer is short-circuited ( Figure 1(c)) [2] and then the value of the impedance load ( [figure omitted; refer to PDF] ) and secondary voltage [figure omitted; refer to PDF] are also equal to zero (in a three-phase transformer, all secondary ends are short-circuited to obtain a balanced short circuit). The equations for the transformer for short-circuit experiment are derived from the general system of [figure omitted; refer to PDF] Application of that system of equations on the equivalent circuit in Figure 1(g) [1, 2] for short-circuit scheme can be determined by primary [figure omitted; refer to PDF] and secondary [figure omitted; refer to PDF] current, magnetizing current [figure omitted; refer to PDF] and the common ems short-circuit [figure omitted; refer to PDF] . One has [figure omitted; refer to PDF] where [figure omitted; refer to PDF] If [figure omitted; refer to PDF] is impedance, its active resistance and reactance of the transformer are [figure omitted; refer to PDF] Impedance of transformer of the short-circuited secondary is reduced on a side of supply-line network.
The corresponding phase diagram is shown in Figures 1(c), 1(d), and 1(e) [2]. As it is seen from this diagram, short-circuit voltage [figure omitted; refer to PDF] is triangle's hypotenuse and catheters are active voltage [figure omitted; refer to PDF] and reactive voltage [figure omitted; refer to PDF] . The angle of voltage [figure omitted; refer to PDF] (or impedance, called short-circuit angle) triangle that graphically displays [8, 9] the short-circuit conditions is stated as a reference for the short-circuit triangle and is [figure omitted; refer to PDF] . By adjusting [figure omitted; refer to PDF] we will get the simpler expressions for the current magnetizing and short-circuit ems: [figure omitted; refer to PDF]
Possible equivalent scheme and short-circuit diagram are presented in Figure 1(c). As with experiments of idling it is not necessary to have any particular active load or higher voltage source [10]. If the frequency has a nominal value of [figure omitted; refer to PDF] , the same values are read as in the experiment of idling, primary current, and power such that a transformer takes [figure omitted; refer to PDF] .
By reading of values [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , and [figure omitted; refer to PDF] which are entered into the diagram as phase voltage functions [figure omitted; refer to PDF] a diagram is obtained which is used for graphic determination of [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , and [figure omitted; refer to PDF] in relation to the primary current values [figure omitted; refer to PDF] .
Power factor is determined from the values [figure omitted; refer to PDF] and [figure omitted; refer to PDF] as [figure omitted; refer to PDF] .
Short-circuit test gives the following values of the transformer in relation to rated current values. The impedance of short-circuit and its active and reactive component from the expression is as follows: [figure omitted; refer to PDF] Active component is a sum of resistance of the two coils [figure omitted; refer to PDF] . During short-circuit test, it should be stressed at which temperature [figure omitted; refer to PDF] the measurement is performed, [figure omitted; refer to PDF] , where the temperature is set at around 75°C, where [figure omitted; refer to PDF] . Reactive component, [figure omitted; refer to PDF] , is calculated from the sum of inductive scattering, independent currents which are flowing through respective coils [11]. From the same reasons [figure omitted; refer to PDF] is an independent value in accordance with the tested currents [12]. Impedance and power factor in the short-circuit are set for the temperature of 75°C: [figure omitted; refer to PDF]
2.4. Losses [figure omitted; refer to PDF] in the Short-Circuit Test
If the rated currents flow through the coils [figure omitted; refer to PDF] practically there is no difference in the value of losses in copper on the primary and secondary side: [figure omitted; refer to PDF] where the copper losses are several times greater than the losses in the core of the transformer at short-circuit, [figure omitted; refer to PDF] .
Short-circuit voltage is defined as the voltage that must lead to single coil, when in the second short-circuited winding rated current [figure omitted; refer to PDF] flows, which corresponds to the nominal voltage of coils at a temperature of 75°C. If the voltage has been brought to the primary winding, short-circuit voltage is expressed in absolute units [figure omitted; refer to PDF] .
Active and reactive components of short-circuit voltage are obtained by the following expression: [figure omitted; refer to PDF]
3. The Proposed Measurement Method
To determine the two parameters of the impedance sources (in this case resistance [figure omitted; refer to PDF] and inductive reactance [figure omitted; refer to PDF] transformers), it is sufficient to examine only two modes of load. By graph-analytical method, through analysis of vector diagrams of two different passive loads, active and reactive (capacitive/inductive), realistic results can be obtained. It should be emphasized that the application of inductive loads in measurement is not recommended because inductive loads have prominent and active component of resistance that cannot be simply determined (22). The active component of the inductive load also has an impact on the phase stance [figure omitted; refer to PDF] . Therefore, it is better to perform the procedure with a capacitive load in which the influence of components of active resistance is several times lower. From the vector diagrams that correspond to schemes of measurements (active, Figures 2(a) and 2(b), and reactive capacitive/inductive loads, Figures 2(c) and 2(d) [7]) the equation can be written for the general case: [figure omitted; refer to PDF] where [figure omitted; refer to PDF] , [figure omitted; refer to PDF] -ems of transformers are in idling (measured or simulated on the secondary side of the transformer when the load is omitted). The solution of (1) and (2) is as follows: [figure omitted; refer to PDF] By introducing replacements, [figure omitted; refer to PDF]
Figure 2: Scheme and vector diagrams: (a) load [figure omitted; refer to PDF] -active, (b) vector diagram from [figure omitted; refer to PDF] load, (c) reactive [figure omitted; refer to PDF] load, and (d) vector diagram for [figure omitted; refer to PDF] load.
(a) [figure omitted; refer to PDF] load
[figure omitted; refer to PDF]
(b) Diagram from [figure omitted; refer to PDF] load
[figure omitted; refer to PDF]
(c) [figure omitted; refer to PDF] load
[figure omitted; refer to PDF]
(d) Diagram from [figure omitted; refer to PDF] load
[figure omitted; refer to PDF]
The following is obtained: [figure omitted; refer to PDF]
(1) One has [figure omitted; refer to PDF] & [figure omitted; refer to PDF] : [figure omitted; refer to PDF] ; consider [figure omitted; refer to PDF]
(2) One has [figure omitted; refer to PDF] & [figure omitted; refer to PDF] : [figure omitted; refer to PDF] ; consider [figure omitted; refer to PDF]
To determine the value [figure omitted; refer to PDF] in both combinations of [figure omitted; refer to PDF] & [figure omitted; refer to PDF] and [figure omitted; refer to PDF] & [figure omitted; refer to PDF] first replace the value of the reactance [figure omitted; refer to PDF] into (26): [figure omitted; refer to PDF] Equitation has the same form for both combinations, so it can be written with parameters [figure omitted; refer to PDF] , [figure omitted; refer to PDF] : [figure omitted; refer to PDF] (explicit relation) or [figure omitted; refer to PDF] (implicit relation).
Basic type quadratic equation is obtained: [figure omitted; refer to PDF] . After replacing values [figure omitted; refer to PDF] coefficients have following values: [figure omitted; refer to PDF] Second grade equitation (quadratic) with nominal form [figure omitted; refer to PDF] or (after dividing with ( [figure omitted; refer to PDF] )): [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , [figure omitted; refer to PDF] .
The number of real solutions depends on the sign of the discriminant [figure omitted; refer to PDF] , [figure omitted; refer to PDF] if one has the following:
(i) [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , has 2 solutions (2 real roots).
(ii) [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , has 1 solution (2 same roots) [figure omitted; refer to PDF] , [figure omitted; refer to PDF] .
(iii): [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , has 2 solutions (2 complex roots).
Solving of quadratic equitation, one has the following.
(1) Method: one has [figure omitted; refer to PDF]
(2) Method: apply the formula [figure omitted; refer to PDF]
And for the form [figure omitted; refer to PDF] , root characteristic is [figure omitted; refer to PDF] Active electric resistance of electrical sources [figure omitted; refer to PDF] is due to the physical nature of the real value greater than zero [figure omitted; refer to PDF] so the characteristic roots of quadratic equations have to be [figure omitted; refer to PDF] ; [figure omitted; refer to PDF] . This is possible if [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , has two solutions (two real roots or two same roots) and if [figure omitted; refer to PDF] Additional condition is that root value must be [figure omitted; refer to PDF] , where the value for [figure omitted; refer to PDF] can stay real value [figure omitted; refer to PDF] and because it cannot be imaginary value: [figure omitted; refer to PDF] . As it is [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , that condition depends on the value relation [figure omitted; refer to PDF] : [figure omitted; refer to PDF] If the values are [figure omitted; refer to PDF] the values of root's quantity are equal to zero and there is one solution for [figure omitted; refer to PDF] , the value which in principle means that the value of [figure omitted; refer to PDF] ; that is, [figure omitted; refer to PDF] . This is possible if [figure omitted; refer to PDF] or with precondition [figure omitted; refer to PDF] .
4. Simulation Results
In this case, the graph-analytical method for the verification of the simulation method [14], which replaces the measurement method, dry power transformer ABB of coupling [figure omitted; refer to PDF] , power 1; 2; and 3.15 MVA, and the tests with three measurements for active, for capacitive, and for inductive loads are selected (adapted the program psb3phasesignalseq (Figure 3)) [14].
Figure 3: Demonstration of the adapted discrete 3-phase programmable voltage source 3-phase V-I measurement.
[figure omitted; refer to PDF]
Data on the three-phase ABB transformers, obtained by experimental procedure in the laboratory, are taken from [13] and shown in Table 1, with the following values:
Table 1: Table of the transformers of brochure [13].
Power | [figure omitted; refer to PDF] | No-load losses | Load losses (75°C) | [figure omitted; refer to PDF] (Ω) | [figure omitted; refer to PDF] (Ω) | [figure omitted; refer to PDF] (Ω) | |
(kVA) | (kV) | (%) | (W) | (W) | |||
T1ABB 1000 | 10/0.4 | 6% | 2000 | 8800 | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
T2ABB 2000 | 10/0.4 | 6% | 3500 | 15500 | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
T3ABB 3150 | 10/0.4 | 6% | 5200 | 22600 | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
The paper presents the following obtained values: rated power [kVA], nominal voltage, connected voltage, or idle running voltage, on primary-higher voltage HV (kV) [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , and [figure omitted; refer to PDF] and the lower secondary LV (kV) [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , and [figure omitted; refer to PDF] , the impedance value of (%), idle running losses, and losses of loaded transformer at rated current and current at rated load.
Simulations in MATLAB program (Simulink-Power System, psb3phasesignalseq) on ABB transformers are derived from 100% load on [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , and [figure omitted; refer to PDF] with [figure omitted; refer to PDF] [MVA].
Secondary currents are indicated on diagrams [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , and [figure omitted; refer to PDF] and secondary voltages in different load tests with active, reactive capacitive (or inductive) load.
Gained changes of electrical quantities are shown in Figures 4, 5, and 6.
Figure 4: Diagram voltage [figure omitted; refer to PDF] (V) and current [figure omitted; refer to PDF] (A).
(a) No-load
[figure omitted; refer to PDF]
(b) [figure omitted; refer to PDF] (1 MW)
[figure omitted; refer to PDF]
(c) [figure omitted; refer to PDF] (1 MVAr)
[figure omitted; refer to PDF]
(d) [figure omitted; refer to PDF] (1 MVAr)
[figure omitted; refer to PDF]
Figure 5: Diagram voltage [figure omitted; refer to PDF] (V) and current [figure omitted; refer to PDF] (A).
(a) No-load
[figure omitted; refer to PDF]
(b) [figure omitted; refer to PDF] (2 MW)
[figure omitted; refer to PDF]
(c) [figure omitted; refer to PDF] (2 MVAr)
[figure omitted; refer to PDF]
(d) [figure omitted; refer to PDF] (2 MVAr)
[figure omitted; refer to PDF]
Figure 6: Diagram voltage [figure omitted; refer to PDF] (V) and current [figure omitted; refer to PDF] (A).
(a) No-load
[figure omitted; refer to PDF]
(b) [figure omitted; refer to PDF] (3.15 MW)
[figure omitted; refer to PDF]
(c) [figure omitted; refer to PDF] (3.15 MVAr)
[figure omitted; refer to PDF]
(d) [figure omitted; refer to PDF] (3.15 MVAr)
[figure omitted; refer to PDF]
Diagrams (for harmonic size changes, between maximal and effective values applies relation [figure omitted; refer to PDF] , [figure omitted; refer to PDF] ) of currents and voltage for a combined test with active and capacitive loads as well as Table 2 which entered all the important values from diagrams and corresponding values are required for the calculation of active resistance and reactance of the transformer. From Tables 1 and 2 the deviation can be seen between the results of measuring the value of [figure omitted; refer to PDF] , [figure omitted; refer to PDF] , which are stated in the ABB manual and those obtained through simulations and they are different to 20% for the results of a reactance and up to 5% for the results of active resistance for all three tested transformer.
Table 2: Results of values and parameters calculated using the graph-analytical method.
Parameters | [figure omitted; refer to PDF] , [figure omitted; refer to PDF] | [figure omitted; refer to PDF] , [figure omitted; refer to PDF] | [figure omitted; refer to PDF] , [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | 3264 | 3264 | 3264 |
[figure omitted; refer to PDF] | 106537 | 106537 | 106537 |
[figure omitted; refer to PDF] | 3231 | 3231 | 3232 |
[figure omitted; refer to PDF] | 104393.6 | 104329 | 104458 |
[figure omitted; refer to PDF] | 2000 | 4000 | 6400 |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | 350 | 350 | 350 |
[figure omitted; refer to PDF] | 122500 | 122500 | 122500 |
[figure omitted; refer to PDF] | 2200 | 4400 | 7000 |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | 2 | 2 | 2 |
[figure omitted; refer to PDF] | 0.2961 | 0.148 | 0.0919 |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | 1.35-10-3 | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
[figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] | [figure omitted; refer to PDF] |
Diagrams (for harmonic size changes, between maximal and effective values applies relation [figure omitted; refer to PDF] , [figure omitted; refer to PDF] ) of currents and voltages for combined test with active and inductive load for all three transformers are shown in the paper, but because of the volume and significant values of diagrams for active resistance and reactance of the transformer the table is not displayed.
5. Conclusions
Graph-analytical method can be used not only to determine the active and inductive AC power source parameters but also to determine and analyze the impendence of electrical sources with high frequencies or in a transient process. It should be emphasized that it is better to determine parameters of transformer or source from measuring or simulation test combined with [figure omitted; refer to PDF] and [figure omitted; refer to PDF] loads that are close to the nominal load, where the errors are minimized. Larger deviations in the measurement or simulating values occur when calculating the reactance, which is natural, because the reactive loads are usually combined with a significant presence of the active component (lower value with capacitive and higher value with inductive loads).
Conflict of Interests
The authors declare that there is no conflict of interests regarding the publication of this paper.
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Copyright © 2015 Zorica Bogicevic et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
This paper presents a graph-analytical method for determining the electrical impedance of alternate energy sources, especially small power transformers and current transformers in electric networks. Unlike conventional short-circuit and idle tests, according to proposed method, in this paper, transformer parameters are determined in a new way, which is based on measurement of voltages and currents on the active and reactive load (inductive or capacitive). The effectiveness of the proposed model was verified using an adapted simulation in the software package MATLAB Simulink. The simulation was performed for three types of ABB transformers with a 100% load. Simulation results were obtained for power transformers: [subscript]Sn1[/subscript] =1 [MVA], [subscript]Sn2[/subscript] =2 [MVA], [subscript]Sn3[/subscript] =3.15 [MVA]. If we compare measurement result values of [subscript]RT[/subscript] , [subscript]XT[/subscript] , which are contained in a brochure for ABB transformers and those obtained through simulation, different tolerances are obtained. For reactance results, deviations are up to 20% for all three tested transformers. For results of active resistance tolerances are up to 5% for all three tested transformers. This method can be used not only to determine the active and inductive AC power source parameters but also to determine and analyze the impendence of electrical sources with high frequencies.
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Neither ProQuest nor its licensors make any representations or warranties with respect to the translations. The translations are automatically generated "AS IS" and "AS AVAILABLE" and are not retained in our systems. PROQUEST AND ITS LICENSORS SPECIFICALLY DISCLAIM ANY AND ALL EXPRESS OR IMPLIED WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES FOR AVAILABILITY, ACCURACY, TIMELINESS, COMPLETENESS, NON-INFRINGMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Your use of the translations is subject to all use restrictions contained in your Electronic Products License Agreement and by using the translation functionality you agree to forgo any and all claims against ProQuest or its licensors for your use of the translation functionality and any output derived there from. Hide full disclaimer