WO2016178667A1

WO2016178667A1 - Handling faults in multi-phase motors

Info

Publication number: WO2016178667A1
Application number: PCT/US2015/029169
Authority: WO
Inventors: Souvik DASGUPTA; Maksim RADOV
Original assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Current assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Priority date: 2015-05-05
Filing date: 2015-05-05
Publication date: 2016-11-10
Anticipated expiration: 2017-11-05

Abstract

A multi-phase motor for handling faults may provide two phase groups of windings with each of the phase groups providing windings for the multiple phases of the motor. The motor may include several disconnection switches for the two phase groups of windings. The disconnection switches may be associated with a particular phase group and a specific phase of the motor. When a fault is detected in the motor, disconnection switches corresponding to one of the phase groups of windings are switched to an opened state to disconnect the phase group windings and allow the motor to operate with the other phase group windings despite of the detected fault.

Description

HANDLING FAULTS IN MULTI-PHASE MOTORS

BACKGROUND

[0001] This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.

[0002] Electric motors may be used for a variety of purposes at a well site. For example, an electric motor (e.g. electric submersible pumps or ESPs) may be deployed for any variety of pumping purposes. In electric motors, a ground fault or inter-phase short may prevent proper operation of the motor. Electric motors operate with multi-phase balanced supply in the stator to generate air-gap rotating magnetic field. If a ground fault is present in multiple phases of the motor, there may be a short circuit between the grounded phases through the ground. In a direct inter-phase short between the windings, circulating current is created with a higher magnitude, which may result in severe unbalance in the motor currents producing vibration, noise. Also, in the advent of these inter-phase fault, extra current may be drawn from the variable-speed drive (VSD) leading to faster aging or even burning of motor phases, cables and/or other connected accessories. This may also result in the power supply being tripped due to overcurrent or even problems restarting the motor due to overcurrent via a short circuit in motor winding.

SUMMARY

[0003] A motor providing multiple phases may provide two phase groups of windings with each of the phase groups providing windings for the multiple phases of the motor. In some embodiments, the windings of these phase groups may be coupled to common terminals for each phase. Further, the motor may also include several disconnection switches for the two phase groups of windings. The disconnection switches may be associated with a particular phase group and a specific phase of the motor. When a fault is detected in the motor, disconnection switches corresponding to one of the phase groups are switched to an opened state to allow the motor to operate in spite of the detected fault. For example, the current at the start and end of a winding may be compared to determine if there is a difference in the current, thereby indicating that a fault is present. In some embodiments, fault(s) may be detected by using current difference detectors or differential current transformers (DCTs) that monitor the current at the start and end of a winding. In some cases, the motor may be the motor of an electric submersible pump (ESP) deployed in a wellbore. The ESP may be coupled to a power cable provided at a surface of the well.

[0004] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

[0006] Figure 1 illustrates a motor under healthy operation in accordance to an aspect of the disclosure.

[0007] Figure 2 illustrates a motor operating with an inter-phase fault in accordance to an aspect of the disclosure.

[0008] Figure 3 illustrates an electric submersible pump system deployed in a wellbore in accordance to one or more aspects of the disclosure.

[0009] Figure 4 illustrates a multi-phase motor with multiple phase group windings and disconnection switches in accordance to an aspect of the disclosure.

[0010] Figure 5 illustrates an inter-phase fault between phase-a and phase-b in the same phase group in accordance to an aspect of the disclosure.

[0011] Figure 6 illustrates a schematic of an inter-phase fault between phase-a and phase-b in different phase groups in accordance to an aspect of the disclosure.

[0012] Figure 7 illustrates a disconnection switch combined with a current sensor and control switch in accordance to an aspect of the disclosure. [0013] Figure 8 illustrates a schematic of control logic to operate disconnection switches of a first phase group in accordance to an aspect of the disclosure.

[0014] Figure 9 illustrates a schematic of control logic to operate disconnection switches of a second phase group in accordance to an aspect of the disclosure.

[0015] Figure 10 illustrates a control switch in accordance to an aspect of the disclosure.

[0016] Figure 1 1 illustrates a differential current transformer in accordance to an aspect of the disclosure.

[0017] Figure 12 illustrates operation of a motor with an inter-phase fault between phase-a and phase-b in the same phase group in accordance to an aspect of the disclosure.

[0018] Figure 13 illustrates operation of a motor with an inter-phase fault between phase-a and phase-b in different phase groups in accordance to an aspect of the disclosure.

[0019] Figure 14 illustrates an inter-phase fault between two phases and two phase groups in accordance to an aspect of the disclosure.

[0020] Figure 15 illustrates an operating state of a motor in response to the inter-phase fault in accordance to an aspect of the disclosure.

[0021] Figure 16 illustrates a control logic for operating disconnection switches when multiple faults are present in multiple phase groups in accordance to an aspect of the disclosure.

[0022] Figure 17 show a schematic of an arrangement for gauge connection. DETAILED DESCRIPTION

[0023] It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

[0024] As used herein, the terms connect, connection, connected, in connection with, and connecting are used to mean in direct connection with or in connection with via one or more elements; and the terms couple, coupling, coupled, coupled together, and coupled with are used to mean directly coupled together or coupled together via one or more elements. As used herein, the terms up and down; upper and lower; top and bottom; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth being the lowest point, wherein the well (e.g., wellbore, borehole) is vertical, horizontal or slanted relative to the surface.

[0025] Figures 1 and 2 are schematic illustrations of an electric circuit of a motor for example in a submersible pumping system, generally denoted by the numeral 20. In the illustrated examples, a motor 24 is electrically connected to a power source 50 through an electrical conductor 44. Power source 50 may for example be a variable speed drive. [0026] Figure 1 illustrates the three-phase motor 24 under healthy operation. However, if there is ground fault in two of the three-phase motor stator winding, an internal current flowing loop can be created, as this multi-phase ground fault manifests as inter-phase fault in the motor. Figure 2 illustrates the motor 24 under inter-phase fault in phase-a and phase-b, illustrated by the dashed line 52. With a ground fault in both phase-a and phase-b of the motor, internal closed loops 54 are created. Similarly, a closed loop can be created with a direct inter-phase short circuit fault. The ground faults or inter-phase short circuits can result in huge asymmetry in three-phase currents, e.g. i_a, and i_c. This may lead to vibration and extra thermal loss in the motor/cable resulting in undesirable extra heating. Further, a surface power supply 50 may trip due to over current. Additionally, the system may not restart due to overcurrent from the fault.

[0027] Multi-phase motors and methods for addressing ground faults or inter-phase faults are disclosed herein. A motor may provide multiple phase groups of windings. In some embodiments, the multiple phase groups may be fed from the same motor lead or terminal. The methods and apparatuses may perform an automatic feed disconnection of one of the phase groups at the advent of a fault in any of the phase groups, thereby clearing the short. The automatic disconnect feature may be provided by disconnection switches coupled to the phase groups. With the automatic disconnection features when a fault present, the motor will be able to continue operating with one phase group of stator windings even with the fault.

[0028] For purposes of illustration, examples discussed herein may refer to electric submersible pumps (ESPs). However, it shall be understood that the ESPs in such examples may be replaced by any suitable motor, including motors utilized in other types of well equipment or tools. [0029] Referring generally to Figure 3, an embodiment of a submersible pumping system 20, such as an electric submersible pumping system, is illustrated. Submersible pumping system 20 may comprise a variety of components depending on the particular application or environment in which it is used. Examples of components utilized in pumping system 20 comprise at least one submersible pump 22, at least one submersible motor 24, and one or more motor protectors 26 that are coupled together to form the submersible pumping system.

[0030] In the example illustrated, submersible pumping system 20 is designed for deployment in a well 28 within a geological formation 30 containing desirable production fluids, such as petroleum. A wellbore 32 is drilled into formation 30, and, in at least some applications, is lined with a wellbore casing 34. Perforations 36 are formed through wellbore casing 34 to enable flow of fluids between the surrounding formation 30 and the wellbore 32.

[0031] Submersible pumping system 20 is deployed in wellbore 32 by a deployment system 38 that may have a variety of configurations. For example, deployment system 38 may comprise tubing 40, such as coiled tubing or production tubing, connected to submersible pump 22 by a connector 42. Power is provided to the at least one submersible motor 24 via a power cable 44. The submersible motor 24, in turn, powers submersible pump 22 which can be used to draw in production fluid through a pump intake 46. Within submersible pump 22, a plurality of impellers is rotated to pump or produce the production fluid through, for example, tubing 40 to a desired collection location which may be at a surface 48 of the Earth.

[0032] As a non-limiting example, an ESP motor may be coupled to a 3 -phase power signal via a balanced inductor network having a neutral, ungrounded node, which may be referred to as a "wye node" or "wye point" of the ESP motor. Voltage and current levels of the 3 -phase AC power signal provided by a power supply to an ESP motor may be, for example, of the order of several kilovolts or more and tens of amperes or more, and the signal may oscillate at a frequency on the order of about 60 Hz.

[0033] In some cases, adjustments may be made to an ESP with a variable-speed drive (VSD) unit 50. As an example, a VSD unit can include an ESP controller (e.g. UniConn™ controller marketed by Schlumberger Limited Houston, Texas). A VSD unit with an ESP controller may allow for varying motor speed, which may in turn provide better management of power, heat, or the like. In some instances, an ESP may be deployed with one or more sensors (e.g., a gauge or gauges). Communication of information with other equipment may occur via a power cable, such as in deep wells where the length of a cable or cables may be on the order of several kilometers.

[0034] It should be noted the illustrated submersible pumping system 20 is only one example of many types of submersible pumping systems that can benefit from the features described herein. For example, other components can be added to the pumping system, and other deployment systems may be used. Additionally, the production fluids may be pumped to the collection location through tubing 40 or through the annulus around deployment system 38. The submersible pump or pumps 22 also can utilize different types of stages, such as mixed flow stages or radial flow stages.

[0035] In one embodiment, a motor may be any suitable multi-phase motor. The motor may be driven by a multi-phase power supply providing a multi-phase AC power signal. The motor may provide multiple phase groups for the multi-phase windings. Each of the phase groups may provide windings for each of the different phases provided by the multi-phase motor. As a non- limiting example, the motor may provide two phase groups of three-phase windings.

[0036] In some embodiments, the motor may provide an automatic disconnect feature that is triggered by a fault, such as ground fault or inter-phase fault, in any of the phases in any of the phase groups. The faults may be detected comparing the current at the start and the end of a winding. When a motor is operating properly, the currents at the start and end may be the same. However, when the current at the start and end of the winding is different, a fault may be present in the winding. In some embodiments, the faults may be detected utilizing current difference detectors or differential current transformers (DCTs). The automatic disconnect feature may disconnect one of the multiple phase groups when a fault is detected, and as a result, it clears the short circuit and allows the motor to continue operating with one phase group. In some embodiments, the automatic disconnect feature may implemented utilizing one or more disconnection switches, controlled switches, intelligent fuses, or the like.

[0037] In some embodiments where the disconnection switch is realized with controlled switch, the control logic of the switching may be implemented using downhole gauge or any other downhole control unit. In embodiments where the disconnection switch is implemented using an intelligent fuse, the switching may be based on the extra thermal generation due to a short circuit.

[0038] Figure 4 illustrates a multi-phase motor 24 with automatic disconnect features. The motor provides a stator that has two phase groups 410-1 and 410-2, where each phase group has three-phase windings 420-1 and 420-2. Group 1 : Phase-a: aiNi, Phase-b: biNi, Phase-c: CiNi; and Group 2: Phase-a: a₂N₂, Phase-b: b₂N₂, Phase-c: c₂N₂.

[0039] In some embodiments, each phase of the phase group 410-1 and 410-2 may be coupled to a common motor lead or terminal (e.g. a, b, or c). Each phase of the phase groups 410-1 and 410-2 provides automatic disconnect features 430-1 and 430-2. In some embodiments, automatic disconnection features 430-1 and 430-2 corresponding to each of the phase groups 410-1 and 410-2 may be provided at the start and end of the windings for each phase. In a non- limiting embodiment, the automatic disconnect features 430-1 and 430-2 may be provided using disconnection switches. For example, the automatic disconnect features 430-1 and 430-2 may be provided by disconnection switches S_xyz, such as controlled switch, intelligent fuse, or the like. The first subscript 'x' indicates the phase a, b or c; second subscript 'y' indicates the phase group 1 or 2; and last subscript 'z' indicates whether the switch is at the start (1) or end (2) of the winding. For example, Sb22 is placed at phase-b, group-2 at the end (2) of the winding. A similar nomenclature is utilized for currents at each disconnection switch i_xyz where, as before, the subscripts represent the phase, phase group, and start/end of a winding respectively.

[0040] In some embodiments, the features of the different phase group windings may include one or more of the following: (1) the same phase of each phase group winding placed in the same slot or different slot of the stator; the neutral point of the two phase group winding Ni and N_? are not connected; (3) each phase of each phase group may be designed for three-phase currents at the motor-cable terminal (e.g. i_a, h and i_c at terminals a, b, and c in Figure 4); and (4) the disconnection switch S_xyz can be a controlled switch, intelligent fuse, or the like.. [0041] The same phase of each phase group winding may be placed in the same slot or different slot of the stator. If placed in the same slot, the magnetic axis coincides. However, if they are placed in phase shifted slot, the same phase shift appears between the magnetic axes of the respective same phase of each group. In some embodiments the neutral point of the two phase group winding Ni and N₂ are not connected. However, the neutral point can be connected during healthy operation of the motor. In some embodiments each phase of each phase group may be designed for three-phase currents at the motor-cable terminal (e.g. i_a, h and i_c at terminals a, b, and c in Figure 4). In a healthy condition, each phase current at a winding for one phase may be approximately half of the motor-cable terminal current. However, during discontent states, the entire current at the motor-cable terminal may run through the winding for one phase. The disconnection switch S_xyz can be a controlled switch, intelligent fuse, or the like.

[0042] The automatic disconnect features may disconnect one of the phase groups when a fault present so that motor can continue operation with the remaining connected phase group of windings. Figures 5 and 6 illustrate two types of inter-phase faults in multi-phase motor 24. Both illustrations show a fault between phase-a and phase-b of a three-phase motor, with Figure 5 showing a fault 512 within the same phase group and Figure 6 showing a fault 612 between two different phase groups. In some embodiments, disconnection switch may be a controlled switch or 'intelligent fuse.' When a controlled switch is utilized, operation may be controlled in accordance with the current passing through the switch. Whenever a fault (e.g. 512 or 612 in Figures 5-6) is present, the current at the start and end of a winding is different. For example, in reference to Figure 5, currents i_aii and i_an are different when a fault is present. However, in healthy condition these currents are same. The same would be true for any other phase in an inter-phase fault state.

[0043] Figure 7 shows a schematic of a controlled switch based disconnection switch. In some embodiments, control switch, S_xyz or 5, may be a combined current sensor 714 and controlled switch 716. Each control switch may sense the current thorough it and may send the current sensor output 718 to a controller.

[0044] Figures 8 and 9 are schematic illustrations of operational logics for disconnection switches in the system. Reference number 7 denotes an "and" gate, number 9 an "or" gate, and number 11 a "not" gate. Disconnection switches corresponding to one phase group windings (represented by 'y' subscript) may be operated with a common control signal, e.g., S_y. Figure 8 illustrates a control logic 800 for disconnection switches in Phase Group 1. Currents at the start and end of windings of each phase (e.g. i_aii and i_an) are paired together and fed to current difference detectors 818. An output (e.g. O_xy, where Y represents the phase and 'y' represents the phase group) from each of the current difference detectors corresponds to the difference in current at the start and end of the winding (e.g. if (i_aii - ian) == 0, O_ai = 1; else O_ai = ø). Anytime there is difference in any of the currents in both ends of a winding in the phase group (e.g. i_aii - i_ai₂≠ 0), the outputted control signal (e.g. Sy) may trigger the opening of the disconnection switches of phase group.

[0045] Figure 9 illustrates control logic 900 for disconnection switches in Phase Group 2. The arrangement is similar to the control logic for Phase Group 1 , but with current difference detectors 918 being fed with currents at the start and end of windings of each phase for Phase Group 2. In some embodiments, a delay 922 may be provided before opening the disconnection switches of one of the phase groups. In the case of inter-phase fault between two phase groups (e.g. see Figure 5), this prevents both sets of disconnection switches for the two phase groups from both being opened at the same time. For example, a delay 922 associated with initiation of S_/=0 and ¾=0 may be provided to ensure that the disconnection switches for both phase groups are not disconnected together. Instead a check may be performed to prevent simultaneous disconnection. For example, the control logic may compare the control signals for the phase groups and open the switches for group 1 when there is an inter-phase fault between phase groups. Notably, in other embodiments, the control logic may be modified so that switches for group 2 may be opened when there is an inter-phase fault between phase groups. Further, another set of control logic may be provided to latch Si or ¾ to zero once any of these becomes zero to ensure the same fault does not return again.

[0046] Figures 10 and 11 respectively illustrate a controlled switch 13 used as a disconnection switch, and a differential current transformer (DCT) for detecting a fault. In some embodiments, simple switches and DCTs may be utilized to provide the control logic. The controlled switch 13 based disconnection switch 1016 may be simple control switch receiving control signal S_y. The DCT 1 124 (Figure 11) may detect whether a fault is present in a particular phase (e.g. phase-a of group 1). In some embodiments, DCTs 1124 may be used in place of the current difference detectors described with reference to Figures 8 and 9. The corresponding windings 1120 of the phase (e.g. windings corresponding to i_aii and i_ai2) pass through a DCT 1 124, thereby providing output from the DCT (e.g. O_ai) that is associated with whether a fault is present. The arrangement shown illustrates a DCT for phase-a of group 1; however, five more DCT with a similar arrangement corresponding to the other phases and groups would be used to replicate the full control scenario shown in Figures 8-9.

[0047] In some embodiments the disconnection switching may be provided by intelligent fuses. The intelligent fuses may be configured such that when there is an extra circulating current, it gives rise to adequate i r loss to open the respective phases or open the fuse. Fuses may be a cost effective way to provide the disconnection switching.

[0048] Figures 12 and 13 respectively illustrate operation of motor 24 with an inter-phase fault between phase-a and phase-b. In Figure 12, an inter-phase fault 1212 is present between the same phase group, whereas Figure 13 shows an inter-phase fault 1312 between the two different phase groups. In both the cases, the group 1 windings 1210-1 or 1310-1 of the stator are disconnected 1230-1 or 1330-1 (illustrated by gaps in the windings, as disconnection switches are omitted for the sake of clarity), which allows the motor to keep running symmetrical current with the group 2 windings 1210-2 or 1310-2 of the motor. In some embodiments the control logic may be altered to disconnect group 2 windings 1210-2 or 1310-2 and run on group 1 windings 1210-1 or 1310-1 if desired. Note that the currents in the group 2 stator windings 1210-2 or 1310-2 remaining connected are increases by about double to cater the load torque without significant change in cable current.

[0049] While the examples shown in Figures 12 and 13 illustrate disconnection 1230-1 or 1330- 1 of switches at both the start and end of the windings of a motor 24, other embodiments may disconnect the switches in a variety of different combinations. In some embodiments, at least one disconnection, at either the start or end of the winding, may be provided in each phase of the group windings to be disconnected. As non-limiting examples, when it is desirable to disconnect group 1 windings, the switches at the start of the group 1 windings may be switched to an open state; the switches at the end of the group 1 windings may be switched to an open state; or a combination of the switches at the start or of the group 1 windings may be switched to an open state.

[0050] Figure 14 illustrates an inter-phase fault 1412 in phase-a and phase-b of group 1 and phase-b of group 2 in a motor 24, and Figure 15 illustrates the disconnection 1430-1 of group 1 windings to ensure no inter-phase fault in motor 24. If there are multiple faults present in the system, a controller may estimate which phase group has the greater number of total faults and disconnect that specific phase group accordingly. For example, Figure 14 shows ground faults 1412-1 and 1412-2 in two of the windings (between i_all and i_an and i_bii and i_bn) in the first phase group Ni and another fault 1412-3 at one winding (between i_b2i and ^22) in second phase group N₂ or direct inter-phase fault. As shown in Figure 15, the windings of phase group Ni may be disconnected 1430-1 (disconnection switches are omitted for the sake of clarity) to address the faults and to allow the motor to continue proper operation.

[0051] Figure 16 is a schematic illustration of a control logic 1600 to operate disconnection switches when multiple faults in the phase groups. The control logic can be used regardless of whether the faults are ground or direct inter-phase faults. The number of faults detected by current difference detectors 1618 from a first phase group may be tallied as a first total ni, and the number of faults detected by current difference detectors 1618 from a second phase group may be tallied as a second total ri₂. The totals ni and ri₂ may be compared 1632, and the phase group with the greatest number of faults present may be switched off. When number of faults in both phase groups is equal, either one of the phase groups may be switched off. As discussed previously regarding other control logic, some embodiments may utilize DCTs to provide current difference monitoring.

[0052] Isolation of two phase group neutrals Ni and N . Illustrating the viability of the systems and methods discussed herein, simulation results suggest that when there is no inter-phase fault in the motor, there is no voltage difference between the two phase group neutrals, Ni and N₂. However, whenever there is an inter-phase fault (specifically within different phase group), the voltage difference between the two neutrals, Ni and N₂ increases noticeably as suggested by simulation results. This is also trivial from the consideration that inter-phase fault develops asymmetry between the phase groups manifesting as voltage difference between the phase group neutrals, Ni and N₂. Since the two neutrals are of different voltage during fault, gauge connection can be done using both the neutrals.

[0053] Figure 17 illustrates a gauge connection arrangement 1700. The methodology provides a high impedance connection 1710 (using high resistance, high inductance, or a combination thereof) between the two neutrals Ni and N₂ and gauge 1720 is connected by tapping middle of the high impedance. In a healthy condition, both the neutrals Ni and N₂ have the same potential and gauge 1720 operation is normal. When a fault happens, a voltage may be present between the neutrals and the high impedance connection 1710 prevents high power frequency current. In this fault condition, gauge 1720 receives controlled operating voltage by means of the impedance. When the fault is cleared, one of the neutral is inactive due to disconnection of one of the phase groups and gauge operation remains uninterrupted due to the configuration. [0054] The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term "comprising" within the claims is intended to mean "including at least" such that the recited listing of elements in a claim are an open group. The terms "a," "an" and other singular terms are intended to include the plural forms thereof unless specifically excluded.

Claims

WHAT IS CLAIMED IS:

1. A method for handling faults in a motor, the method comprising:

operating a motor with multiple phases, the motor comprising:

a first group of windings, wherein each winding of the first group of windings corresponds to one of the multiple phases of the motor;

a second group of windings, wherein each winding of the second group of

windings corresponds to one of the multiple phases of the motor, and a first and second set of disconnection switches, wherein the first set corresponds to the first group of windings and the second set corresponds to the second group of windings;

monitoring the windings of the first group and the second group for a fault; and switching at a switch for each phase of the multiple phases of the first set of

disconnection switches or the second set of disconnection switches to an open state when the fault is detected.

The method of claim 1 further comprises:

monitoring a current at a start and end of each winding of the first and the second

of windings; and

indicating a detected fault when the current at the start and end of one winding is

different.

3. The method of claim 2, wherein the current is monitored by a plurality of current difference detectors or differential current transformers (DCTs).

4. The method of claim 1, wherein the first or second set of disconnection switches in the open state correspond to a group of windings that the fault is detected in.

5. The method of claim 1, further comprising:

determining a total number of faults detected for each of the first and the second group of windings;

comparing the total number of faults detected for each of the first and second group of windings; and

opening the first or second set of disconnection switches corresponding to a group of windings with a greatest total number of faults.

6. The method of claim 1, wherein the first and second set of disconnection switches are controlled switches or intelligent fuses.

7. The method of claim 1, wherein the motor is connected to an electric submersible pump (ESP).

8. A motor providing multiple phases, the motor comprising: a first group of windings, wherein each winding of the first group of windings corresponds to one of the multiple phases of the motor;

a second group of windings, wherein each winding of the second group of windings corresponds to one of the multiple phases of the motor;

a first set of disconnection switches, wherein each phase of the first group of windings is coupled to one of the first set of disconnection switches; and

a second set of disconnection switches, wherein each phase of the second group of

windings is coupled to one of the second set of disconnection switches, and when a fault is detected, at least one switch for each phase of the multiple phases of the first set of disconnection switches or the second set of disconnection are switched to an opened state.

9. The motor of claim 8, wherein each winding of the second group of windings is coupled to a terminal that is coupled to one of the first group of windings with an identical phase.

10. The motor of claim 8, further comprising a plurality of current difference detectors, wherein each of the plurality of current difference detectors monitors a current at a start and end of one winding of the first or the second group of windings, and the fault is detected when the current at the start and end of the one winding is different.

11. The motor of claim 8, further comprising a plurality of differential current transformers (DCTs), wherein each of the plurality of DCTs monitors a current at a start and end of one winding of the first or the second group of windings, and the fault is detected when the current at the start and end of the one winding is different.

12. The motor of claim 8, wherein the first or the second set of disconnection switches that are in the opened state correspond to a group of windings that the fault is detected in.

13. The motor of claim 8, wherein a total number of faults for each of the first and the second group of windings is determined, and a set of disconnection switches corresponding to a group of windings with a greater total number of faults are switched to the opened state.

14. The motor of claim 8, wherein the first and second set of disconnection switches are controlled switches or intelligent fuses.

15. The motor of claim 8, wherein the motor is connected to an electric submersible pump (ESP).

16. An electric submersible pumping (ESP) system, the system comprising a motor coupled to a power cable, the motor comprising:

a first group of windings, wherein each winding of the first group of windings

corresponds to one of multiple phases of the motor; a second group of windings, wherein each winding of the second group of windings is coupled to a terminal that is coupled to one of the first group of windings with an identical phase;

17. The system of claim 16, further comprising a plurality of current difference detectors, wherein each of the plurality of current difference detectors monitors a current at a start and end of one winding of the first or the second group of windings, and the fault is detected when the current at the start and end of the one winding is different.

18. The system of claim 16, further comprising a plurality of differential current transformers (DCTs), wherein each of the plurality of DCTs monitors a current at a start and end of one winding of the first or the second group of windings, and the fault is detected when the current at the start and end of the one winding is different.

19. The system of claim 16, wherein the first or second set of disconnection switches that are in the opened state correspond to a group of windings that the fault is detected in.

20. The system of claim 16, wherein a total number of faults for each of the first and the second group of windings is determined, and a set of disconnection switches

corresponding to a group of windings with a greater total number of faults are switched to the opened state.