challenges of protection systems in distribution networks ... · source: ieee std. 3002.3-2018. 10...

Challenges of Protection Systemsin Distribution Networks

considering DER

Juan Manuel Gers, PhD

September 30th 2020

Content

• Introduction

• High level comparison of US and Colombian systems

• Protective relay in systems with DERs

• Adaptive Protection during changing system conditions

• Conclusions

Introduction

Nonrenewable Energy

Renewable Energy

Nuclear Energy

Coal Energy

Oíl Energy

Gas Energy

Biomass Energy

Solar Photovoltaic Energy

Solar Thermal Energy

Hidraulic Energy

Ocean Thermal Energy

Wind Energy

Tidal Energy

Sea Waves Energy

Geothermal Energy

5

Photovoltaic systems are connected via DC/AC power electronics modules to the grid

Technology

Inversor

National Grid

PV Generation

Typical layout of a PV system

PV Power Plant

MPPT PWMReactive

powercontroller

AC FILTER

=~

Fire angle Amplitude

𝑄𝑃𝑉𝑈𝐷𝐶𝐼𝐷𝐶

𝑍𝑆 𝐸𝑆

A photovoltaic system consists of anarrangement of several componentsto absorb and convert sunlight intoelectricity and a solar inverter tochange the electric current from DCto AC.

It may also use a MPPT system toimprove the system's overallperformance.

MPPT: Maximum Power Point TrackingPWM: Pulse Width Modulation

Wind Generation

Circuit diagram of a Type 1 generatorFixed-speed WT

Circuit diagram of a Type 3 generatorDoubly-fed induction generator WT

Circuit diagram of a Type 2 generatorVariable-slip WT

Circuit diagram of a Type 4 generatorFull-converter WT

9

Technology(DC synchronous generator behavior)

Source: IEEE Std. 3002.3-2018

10

Technology(DC photovoltaic system behavior)

Source: Fault current contribution from wind plants - IEEE PRSC

Considerations of Fault Current Contributions

Considerations under fault conditions:

• Inverters: 1.2 to 1.5 times the rated load current.

• Synchronous generator: the fault contribution can reach more than six timesthe generator full-load current.

Content

• Introduction


• Protective relay in systems with Renewables


• Conclusions

High level comparison of US and Colombian systems

Department of Energy

Federal Energy Regulatory Comission

Many Vertical Monopoloy Transmission OperatorsMany ISOs/RTOsThe ISO/RTO Council

North American Electric Reliability Corporation

The US Regulatory & Market Scheme

NERC■ ASCC Alaska Systems Coordinating Council

■ WECC Western Electricity Coordinating Council

■ MRO Midwest Reliability Organization■ SPP Soutwest Power Pool■ TRE Texas Reliability Entity■ NPCC Northeast Power Coordinating Council■ RFC Reliability First Corporation■ SERC SERC Reliability Corporation■ FRCC Florida Reliability Coordinating Council

The US Regulatory & Market SchemeVertical Monopoly Example

Each Utility has:• Some generation units• Transmission• Distribution• Costumers• TSO rights

The US Regulatory & Market SchemeRegulatory responsibilities

High level comparison of US and Colombian systems

Differences between* Highlights

MinMinas DOE Both define responsibilities and policies for other organizations and entities.

CREG FERC/NERC

• CREG has a smaller market, regulates nation-wide• FERC regulates only interstate markets• NERC regulates technical aspects for planning and operation• USA has 50 different markets• Each state has its own regulations (e.g. FL’s Public Service Commision)• Each state can change FERC regulations to a certain degree

UPME NERC

• NERC is made up from nine big reliability entities.• NERC is a non-government organization, but it is an international regulatory authority• UPME makes proposals for CREG regulatory updates, NERC develops and enforces reliability

standards• Term planning

• UPME to mid and long term• NERC to short and long terms

XM IRC• XM is the sole ISO for Colombia• IRC integrates every USA’s ISO into a single voice for desition-making and participation

* Same row entities are not purely equivalent, as shown

Content

• Introduction




• Conclusions

System Protection with DER’s

Protectionsystem

Reliability

Response speed

Selectivity

Flexibility

Impacts of DERs on Protection

• A traditional distribution system is a radial one-end-source system,• The present DGs also contribute to the fault current• Changes on the short-circuit level• Type, location and capacity of the DG affects the operation of the relay

in the distribution network.

Source: Fusheng, L Microgrid Technology and Engineering Application. 2016

Challenges of DERs in Protection Systems

• Blindness of Protection• Unsynchronized Reclosing • Miscoordination• False Tripping

Main impacts

Source: L. Che. Et al. 2014A. Hooshyar. 2017

Synchronization Parameter Limits

Source: IEEE Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric PowerSystems Interfaces," in IEEE Std 1547-2018 (Revision of IEEE Std 1547-2003) , vol., no., pp.1-138, 6 April 2018, doi:10.1109/IEEESTD.2018.8332112.

DER Response to Abnormal Frequencies


Frequency Ride-through Requirements for DERs


System Protective Responses- OOS

• PRC-024-2 Voltage and Frequency• OOS Based on the responses of multiple

elements along the power system

PSB of distance and underimpedanceprotection

PSP of synchronous generators

OST in transmission lines

-0.60

-0.10

0.40

0.90

-0.40 0.10 0.60 1.10 1.60

Rea

ctan

ce (p

.u.)

Resistance (p.u.)

Path of Z in the plane R-X

Contingency_1Contingency_2

Power System Studies

PRC-024-2Protective Set-Up

Protective relay in systems with Renewables

Solar Panels are normally arranged in Strings. These can be connected inparallel to form a set of strings.

Arrays are either strings connected in parallel either individually or in blocks ofstrings

- + - + - +

- + - + - +

String 1

String 2

Array

-+

Combiner box


+

-

Solar modules String combiner

DC Connection +

-

Sub-array combiner

Array fuse links


Each individual string has to have fuses at both the positive and negativeends. Likewise, each array has to have fuses at both the positive andnegative terminals.

The criteria to select fuse links for string protection when number of strings inparallel is higher than 3 according to the IEC 60269-6 are:

• Voltage rating: ≥ 120% the open circuit voltage times the number ofmodules in series per string.

• Current rating: ≥ 156% the short circuit current, but no more than thePV module maximum overcurrent protection rating specified by IEC61730-2.

Case Example of a 20 MVA Solar Farm

One PV array consists of 504 PVPanels organized in 24 strings of21 modules.

Five PV arrays are connected tothe DC input of the correspondinginverter.

Two inverters are connected toeach power transformer. Thereare 10 power transformers perloop.

The plant has two MV Loops.

1 PV Panel = 235 W

21 panels / string x 235 W = 4,935 W / string

24 strings / array x 4935 W / string = 118,440 W / array

5 array / inverter x 118440 W / array = 592,200 W / inverter

2 inverter / transformer x 592200 W / inverter = 1,184,400W per transformer.

10 power transformers x 1,184,400 W / transformer= 11,844,000 W per loop.

2 loops x 11,844,000 W / loop = 23,688.000 W @ plant

Plant Power = 23.69 MW

Case Example of a 20 MVA Solar Farm

24 String Connections PV Panels connected in series

General Single Line Drawing for one 20 MVA Solar PV Plant

Case Example of a Solar Farm

Single Line Drawing showing AC-DC connection


• MV Switchgear

• Three winding Transformer: 1 MVA, 13.2 kV / 2 x 200 V

• Inverters, 1000 V, 600 kVA each.

• DC Fuses, 350 A, 1000 V.

• 5 arrays connected to each inverter.

• 1 array is composed 24 strings connected in parallel.

• 1 string is composed of 21 PV solar panels connected in series. There are 504 PV modules per array.



Large Machine Protection IEEE C37.102-2006


Recommended protective scheme for wind farmsFunctional Block Diagram

52

27X 59X 59N 60V 59 27

87

50P 51V 46 50BF 67P

50G 51G 67G

32 32R 32L

50N 51N 67N

81U 81O VTFF


SECTION DESCRIPTIONZone-1 = smaller of the two following criteria:1. 120% of unit transformer2. 80% of Zone 1 reach setting of the line relay on the shortest line (neglecting in-feed); time = 0.5 sZone-2 = the smaller of the three following criteria:A. 120% of longest line (with in-feed). If the unit is connected to a breaker and ahalf bus, thiswould be the length of the adjacent line.B. 50% to 66.7% of load impedance (150% to 200% of the generator capabilitycurve) at the RPFAC. 80% to 90% of load impedance (111% to 125% of the generator capabilitycurve) at themaximum torque angle; time > 60 cycles

Note: Maximum load impedance at rated power factor does not encroach intothe reach. A value of 150% to 200% is recommended to avoid tripping duringnormal load. Zone2


Table 1 - Recommended Settings

IEEE No. FUNCTION Per IEEE C37.102 SECTION DESCRIPTION

32 Reverse Power 4.5.5.3 & A.2.9

Pickup setting should be below the following motoring limits: Gas : 50% rated power; time < 60 s Diesel : 25% rated power; time < 60 s Hydro turbines : 0.2% - 2% rated power; time < 60 s Steam turbines : 0.5% - 3% rated power; time < 30 s

40

Loss-of-field Approach # 1

4.5.1.3 & A.2.1

UNIT 1 Offset: X'd/2; Diameter: 1.0 pu; time: 0.1 s UNIT 2 Offset: X'd/2; Diameter: Xd; time: 0.5 to 0.6 s

Loss-of-field Approach # 2

UNIT 1 Offset: X'd/2; Diameter: 1.1 Xd - X'd /2 or 1.25Xd - X'd /2 ; Time: 0.25 s

UNIT 2 Offset: XTG + X min SG1; Diameter: 1.1 Xd + XTG + Xmin SG1 or 1.25 Xd + XTG + Xmin SG1 Time: 1.0 s < t < 60 s.

Angle of directional element = -13o


SECTION DESCRIPTION

46 Negative Sequence Overcurrent4.5.2 & A.2.8

Pickup setting should be below the permissible I2 percent expressed in percent of rated current, which are indicated below:Salient pole: 10% With connected amortisseur windings : 10% With non-connected amortisseur windings : 5% Cilindrical rotor Indirectly cooled : 10%Directly cooled - Up to 350 : 8% - 351 MVA TO 1250 MVA : 8% (MVA-350)/300 - 1251MVA TO 1600 MVA : 5%Permissible K (I22 t)Salient pole generator : 40Synchronous condenser : 30Cylindrical rotor indirectly cooled : 30Cylindrical rotor directly cooled (0 MVA to 800 MVA) : 10 Directly cooled (801 MVA -1600 MVA) : See Figure 4-39

50/87Differential via flux

summation CTs or split-phase protection

4.3.2.5.1The pickup of the instantaneous unit should be set above the CT error currentsthat may occur during external faults. The resulting settings offers little turn faultprotection.

50/27Inadvertent Energization Overcurrent with 27, 81

Supervision

5.4.2.4 & A.2.4

50: pickup ≤ 50% of the worst-case current value and should be > 125% generator rated current.27: 50% Vn, time: 1.5 s


IEEE No. FUNCTION Per IEEE C37.102


SECTION DESCRIPTION

50 BF Generator Breaker Failure Protection4.7 & A.2.11

Current detector: picku should be more sensitive than the lowest current present during fault involving currents.Timer > Generator breaker interrupt time + Curr det. dropout time + safety margin

51N Stator Ground Over-current (Low,Med Z Gnd,Phase CT Residual)

4.3.3.2The grounding resistor is selected to limit the generator's contribution to a single phase-to-ground fault at its terminals to a range of current between 200 A and150% rated full load current

50/51NStator Ground Over-current(Low, Med Z Gnd, Neutral CT or Flux

Summation CT)

51GN, 51N Stator Ground Over-current(High Z Gnd)

4.3.3.1.1

Typically, the overvoltage relay has minimum pickup setting of approximately 5

V. With this setting and with typical distribution transformar ratios, this scheme

is capable of detecting faults to within 2% to 5% of the stator neutral.

50/51 Time overcurrent protection(against overloads)

4.1.1.2

51 pickup: 75-100% FLC, time: 7 s at 218% FLC. FLC means full load current.

50 pickup: 115% FLC, time: instantaneous unit is set to pick up at 115% of full-

load current and is used to torque control the time-overcurrent unit. The

instantaneous unit dropout should be 95% of higher of pickup setting.




SECTION DESCRIPTION

51VC Voltage Controlled Overcurrent4.6.1.2 &

A.2.6

Overcurrent pickup: 50% FLCControl voltage: 75%Vn.Inverse time curve and dial settings should be set to coordinate with system line relays for close-in faults on the transmission lines at the plant.

51VR Voltage Restrained Overcurrent4.6.1.2 &

A.2.6

Overcurrent pickup: 150% FLC at rated voltageInverse time curve and dial settings should be set to coordinate with system line relays for close-in faults on the transmission lines at the plant.

59 Overvoltage 4.5.6. & A.2.12

Relays with inverse time charac and instantaneousPickup: 110%Vn; t= 2.5 s at 140% of pickup settingInst : 130 - 150% VnRelays with definite time charac and 2 stagesAlarm pickup : 110%Vn; 10< t < 15 sTrip pickup : 150% Vn; time: 2 cycles



IEEE No. FUNCTION Per IEEE C37.102 SECTION DESCRIPTION

67IE Directional O/C for Inadvertent Energization

78 Out of Step 4.5.3 & A.2.2

Mho Diameter : 2X'd + 1.5 XTG Blinder distance (d) = ((X'd + XTG + XmaxSG1)/2) x tan (90-(d/2)); d: angular separation between generator and the system which the relay determines instability. If there is not stability study available d = 120º t = as per transient stability study Typically 40 < t < 100 ms

81 Over/under frequency (60 Hz systems) 4.5.8 & A.2.14

Typical Setting 81U ALARM: 59.5 Hz Time: 10 s. The underfrequency load shedding setting in the systems is given as 59.3 Hz with a delay of 14 cycles. 81U TRIP: The generator 81U relay should be set below the pick-up of underfrequency load shedding relay set-point and above the off frequency operating limits of steam turbine.

81O ALARM:Pick-up: 60.6 Hz, Time Delay 5 sec.


SECTION DESCRIPTION

87G Generator Phase Differential 4.3.3.2 & A.2.5Pickup : 0.3 ASlope : 10%time: instantaneous

87GN Generator Ground Differential4.3.2

87UD Unit Differential 4.3.2.6



61

Application Example

62

Application Example

63

Application Example – Internal Fault

65

Application Example

66

Ejemplo de aplicación51V Falla Externa

67

Ejemplo de aplicación51V Falla Externa

Content

• Introduction




• Conclusions

Outage of G2 I’r1 =It1+It2 Ir2 =It1

T1 T2

1

2

3

4

Grid

G1

G2

Loss of a DG Source

t2

Ir2

t’2aR1

Ir1

t1

I’r1

t’1

R2

Normal Condition Ir1 =It1+It2+Ig2 Ir2 =It1

R2a

Coordination is lost in the yellow area unless a setting group change is enabled

Adaptive Protection during changing system conditions

System Protection with DER’s

R-1 R-2

R-DG

RTU

1 2

1 21 2

L-1 L-2

Grid DG

S. Group

S. Group

S. Group

Example of adaptive protection setting with a RTU device

Content

• Introduction




• Conclusions

Conclusions

• Protection schemes of photovoltaic units are based mostly on fuses for both,string and array type modules. Setting procedure is simple to implement andnormally the short circuit level on the busbar is not incremented significantlywhen they are connected.

• Wind generation units are more complex to coordinate than solar units for theprotection coordination.

• The protection scheme of wind generators is similar to those used inconventional generators, which are more elaborate due to the dynamicbehavior of the generators and the complexity of the control systems.

• Consideration of multiple scenarios and topologies must be done to guaranteealways proper protection and selectivity

• Use of multiple setting protection groups is suggested whenever differentscenarios is an option. This requires the application of numerical-type ofrelays.

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Challenges of Protection Systems in Distribution Networks �considering DER ContentIntroductionTechnologyPV GenerationWind GenerationTechnology(DC synchronous generator behavior)Technology(DC photovoltaic system behavior)Considerations of Fault Current ContributionsContentHigh level comparison of US and Colombian systems�The US Regulatory & Market Scheme�The US Regulatory & Market Scheme�Vertical Monopoly ExampleThe US Regulatory & Market Scheme�Regulatory responsibilitiesHigh level comparison of US and Colombian systemsContentSystem Protection with DER’sImpacts of DERs on ProtectionChallenges of DERs in Protection SystemsSynchronization Parameter LimitsDER Response to Abnormal FrequenciesFrequency Ride-through Requirements for DERsFrequency Ride-through Requirements for DERsSystem Protective Responses- OOSProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesCase Example of a 20 MVA Solar FarmCase Example of a 20 MVA Solar FarmCase Example of a Solar FarmCase Example of a Solar FarmCase Example of a Solar FarmProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesProtective relay in systems with RenewablesApplication ExampleApplication ExampleApplication Example – Internal FaultApplication ExampleEjemplo de aplicación�51V Falla ExternaEjemplo de aplicación�51V Falla ExternaContentSlide Number 74System Protection with DER’sContentSlide Number 77Slide Number 78

challenges of protection systems in distribution networks ... · source: ieee std. 3002.3-2018. 10...

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