THE PRINCIPLES OF RELAY PROTECTION IN PROTECTIVE METHOD

SELECT BI FOR LINE PROTECTION (BI7)

The maximum current working through the line L :

 Select BI has the rated current 350A and the rated second current 5A, the rate voltage 22 kV The conversion ratio is n BI 7 = 350

SELECT BI FOR TRANSFORMER PROTECTION

Select BI1 (BI4)

- Current transformer BI1 và BI4 are select with the same the conversion ratio

The maximum current flows through BI1 :

I BI1max = k qt x √ 3 S U dmB Cdm = 1,4 √ 3 110 40 10 3 = 293,92 (A)

 Select BI has the rated primary current 300A and the rated second current 5A, the rate voltage 110 kV The conversion ratio is n BI1 = 300

- Similar, the conversion ratio of BI4 is n BI4 = 300

Select BI2 (BI5)

- Current transformer BI2 và BI5 are select with the same the conversion ratio

Considering the overload condition of the MBA, the maximun current flows through BI1 is:

I BI1max =k qt x √ 3 S U dmB1 Hdm = 1,4 √ 3.22 40 10 3 = 1469,62 (A)

Select BI has the rated primary current 1500 A and the rated second current 5A, the rate voltage 22 kV The conversion ratio is: n BI 2 = 1500 5

- Similar, the conversion ratio of BI5 is : n BI5 = 1500

Select BI3, BI6

We choose BI3, BI6 same BI1 so the ratio is n BI 3 =n BI 6 = 300

Relay protection is a critical aspect of electrical systems, ensuring the safety and reliability of power distribution The principles of relay protection involve detecting faults and isolating affected sections to prevent damage Key methods include overcurrent, differential, and distance protection, each tailored to specific applications and conditions Effective relay protection enhances system stability, minimizes downtime, and protects equipment from potential failures Understanding these principles is essential for engineers and technicians involved in power system management and maintenance.

METHOD OF PROTECTION

METHOD OF PROTECTION FOR TRANSFORMER

2.1.1 The type of faults and abnormal working mode

Fault types can be divided into two groups: internal faults and external faults:

- Touch ground (short circuit) and short circuit ground.

- Oil tankers (oil leak) + External faults:

- Short circuit on the system.

- One-phase short circuit in the system.

 Main protection: Restraint-different relay protection and Buchholz relay

- Function : main protection for transformers

- Protection area: against all types of faults inside the transformer.

+ Restraint differential protection : remove short circuit Single phase or Multi- phases inside transformer

+ Buchholz relay: remove winding faults and oil faults.

 Back-up protection : time overcurrent protection and instantaneous overcurrent protection

- Function : + Back-up protection for transformers + Remove short-circuit faults occuring inside and outside transformer

- Protection area : inside in transformers and a part outside.

- Note : + The impact time of back-up protections must be after the impact time of the main protections

+ Coordinating time with neighboring protections + If the transformer receives power from multiple sources, then put the power orientation at the connection to the source having smaller impact time

+ If there is a two-winding transformer then just put the overcurrent protection at one end of the transformer, near the source (because if one coil is overloaded then

Relay protection principles are essential for ensuring the safety and reliability of electrical systems These principles involve the use of protective methods to detect and isolate faults, particularly in transformers with multiple windings Each winding requires a dedicated set of protective relays to monitor and manage overload conditions effectively By implementing these protective measures, the risk of damage to the transformer and connected equipment is significantly reduced, maintaining system integrity and operational efficiency.

- Function : Ground cover (inner shell) inside the transformer

 Overload protection : Overcurrent or Thermal relay

Figure 2.1 Diagram of protection mode for transformers

METHOD PROTECTION FOR LINE

Line L, classified as a medium voltage line, requires protection against short circuits and accidental contact To ensure safety, we implement a time overcurrent relay (50) as the primary protection mechanism, utilizing Inverse-Time Overcurrent characteristics, while an instantaneous overcurrent relay (51) serves as a redundant backup.

To detect and prevent ground faults on line L, use zero overcurrent relay (50N,

Figure 2.2 Diagram of protection mode for line

The principles of relay protection are essential for ensuring the safety and reliability of electrical systems These principles involve the use of protective relays that detect faults and initiate appropriate actions to isolate affected equipment By employing various protective methods, such as overcurrent and differential protection, relay systems can effectively minimize damage and maintain system stability Understanding these principles is crucial for engineers and technicians to design and implement effective protection schemes, ensuring the continuous operation of electrical networks while safeguarding against potential hazards.

THE PRINCIPLES OF RELAY PROTECTION

RESTRAINT-DIFFERENT RELAY PROTECTION

3.1.1 The principle of restraint-different relay protection

- Directly compare the amplitude of the current at the two ends of the protected element

- Active when the current deviation between two protected elements exceeds a given value (threshold current):

The protective zone for differential protection is defined by the placement of two current transformers at the start and end of the protected element, which capture the current signals for comparison.

Figure 3.1.1 Differential relayprotection a) Diagram of the principle; b) Vector graph of current when short circuit outside the zone and in normal mode; c) short circuit in the area.

In theory =0 However, reality may be different 0 by the effect of unbalanced currents by some of the following reasons:

Current transformer errors can arise from low value inaccuracies and magnetic circuit saturation This saturation typically occurs when the transformer is either unloaded or experiences an external short circuit, leading to significant value fluctuations over a short duration.

The principles of relay protection are essential in ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and isolate affected sections of the network, preventing damage to equipment and maintaining system stability Understanding the various types of relay protection, including overcurrent, differential, and distance protection, is crucial for effective implementation Properly applied, these principles enhance the overall performance of electrical networks and contribute to efficient fault management.

The threshold current is defined as follows: with: =0,1

: homogeneous coefficient BI the same select =1 : noncyclical coefficients, =1,8

: the largest external short circuit

Restraint differential relay protection is differential relay has been added restraint element to increase the sensitivity and reliability of the protection

(With conventional dimension from the busbar to the line)

The threshold current of a restraint differential relay protection system varies based on the current flowing through the protection circuit's branch The relay's comparator component assesses the absolute values of the two currents to ensure accurate monitoring and protection.

When a short circuit occurs outside the protected area, the secondary current vectors I T1 and I T2 exhibit a minimal deviation angle, resulting in the restraint current exceeding the differential current, which prevents the relay from activating.

Relay protection is essential in electrical systems, ensuring the safety and reliability of power distribution This method involves using protective relays to detect faults and initiate corrective actions, preventing damage to equipment and maintaining system stability Understanding the principles of relay protection is crucial for effective implementation, as it encompasses various techniques and technologies designed to safeguard electrical networks By adhering to these principles, operators can enhance the resilience of their systems and minimize the risk of outages or equipment failures.

Figure 3.1.3 Deviation angle between I T1 và I T2 because error of BI

- When short circuit in the protected area: Two vectors I T1 and I T2 have large deflection angle so I SL > I H At that time the relay will work.

- When the power supply from one side: I SL = I H => Relay works

Figure 3.1.4 The impact area of differential protection + Characteristic segment (a):

A low threshold current difference signifies a minimal current deviation in protection against unbalanced currents during normal operation If the line (a) is set too high, it diminishes sensitivity, while a low line (a) can lead to incorrect outcomes.

This feature segment ensures relay operation when considering the BI error.

Characteristic for high braking, ensuring the working of relays when saturating the circuit from BI

Relay protection is a critical component in electrical systems, ensuring the safety and reliability of power distribution This protective method involves the use of relays to detect faults and initiate necessary actions to isolate affected sections of the network Understanding the principles of relay protection is essential for maintaining system integrity and preventing equipment damage Key principles include sensitivity, selectivity, reliability, and speed of operation, which collectively contribute to effective fault detection and isolation By adhering to these principles, engineers can enhance the performance and safety of electrical systems, minimizing downtime and operational risks.

Characteristic for high value deviation.

When the current deviates from this value, the protection will act regardless of the restraint current.

This feature segment relies on the transformer value U N % The threshold is typically established at a point where the short circuit at the transformer output and fault current exceed multiple times the transformer's rated current.

BUCHHOLZ RELAY PROTECTION

- Relays operate based on the evaporation of transformer oil when there is a problem and the level of oil drop is too much.

The Buchholz relay is installed on the pipeline linking the oil tank to the oil extension tank of the MBA This two-level relay features two glass-bulb metal buoys equipped with either mercury or magnetic contacts During normal operation, when the oil tank is full, the floating buoys remain submerged in the oil, keeping the relay contacts in an open position.

In the event of a gas leak or a minor electrical fault, air bubbles form and collect in the Buchholz relay lid Once the accumulated gas reaches a significant level, it causes the float to sink, triggering the relay to issue a level 1 warning.

In incidents involving significant disruptions, such as a touch in multiple wires, a substantial amount of gas is generated, creating a powerful stream that flows through the relays to the expansion tank During this process, the bottom float becomes submerged, leading to the closure of the bottom.

- Thus, the contact on the impact when the incident is minor, affecting signaling.

Contact under the impact when the incident is severe It is arranged to cut the transformer immediately.

Relay protection is a critical aspect of electrical systems, ensuring safety and reliability It involves the use of protective relays to detect faults and initiate corrective actions, minimizing damage to equipment The principles of relay protection include selectivity, sensitivity, and speed, which work together to provide effective fault detection By implementing these principles, systems can maintain operational integrity and prevent cascading failures Understanding the fundamental concepts of relay protection is essential for engineers and technicians in the field, as it directly impacts the performance and safety of electrical installations.

- Protection has two levels: light - signaling and heavy - cutting.

Oil flow relays operate on the same principle as Buchholz relays and are positioned within the regulator load box When an issue arises in this system, the oil heats up and creates a flow, triggering the relay to activate and disconnect the transformers.

TIME OVERCURRENT RELAY

A time overcurrent relay activates with a time delay (∆t) when the current exceeds a predetermined threshold These relays enhance selectivity by adjusting the operating time based on their protection level; the closer the relay is to the power source, the longer the impact time.

- Impact when the current through the protection element exceeds a given threshold:

- Effect against all types of incidents

- Working on the principle of each level, the closer to the source the greater the impact time.

The principles of relay protection are fundamental in ensuring the safety and reliability of electrical systems These principles involve the use of protective relays to detect faults and initiate corrective actions, thereby preventing damage to equipment and maintaining system stability Effective relay protection strategies include the selection of appropriate relay types, settings, and coordination among devices to ensure timely response to electrical disturbances Understanding these principles is essential for engineers and technicians to enhance the performance and resilience of power systems.

Figure 3.3 Time overcurrent protection Thresold current for protection:

- Thresold current of time overcurrent relay selected according to I lvmax passing through the protection element: with:

- k at : the safety factor, k at = 1,1 ÷ 1,2.

- k mm : the opening factor, k mm = 2 ÷ 5.

- k tv : the returning factor, k v = 0,85 ÷ 0,9 with electromechanical relays, k tv =1 with digital relays.

- I lvmax : maximum working current of line

Thresold current of secondary side: with

- K sd : Diagram factor of BI

- n i : the ratio of current transformers

Coordinate with neighborhood protections on the principle of step-by-step ladder.

OVERCURRENT ZERO SEQUENCE PROTECTION

Figure 3.4 Overcurrent Zero sequence protection

- Overcurrent Zero sequence protection also the overcurrent protection so the principle of action is also the effect when the zero sequence current does not exceed the thresold value :

- Overcurrent Zero sequence protection, must place zero sequence current transformer at the neutral of the transformer.

The principles of relay protection are essential for ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and initiate timely corrective actions to prevent equipment damage By utilizing various relay types, such as overcurrent, differential, and distance relays, systems can effectively monitor electrical parameters and respond to abnormalities Understanding these principles is crucial for engineers and technicians to maintain optimal performance and minimize downtime in power distribution networks Implementing robust relay protection strategies enhances the overall resilience of electrical infrastructure.

OVERLOAD TRANSFORMER PROTECTION

Overloading a transformer raises its temperature, and prolonged high overloads can lead to overheating, significantly shortening its lifespan To safeguard power transformers from overloads, conventional overcurrent protection can be employed This system utilizes a current relay designed to detect overload signals and provide necessary protection for the transformer.

Large power transformers utilize thermal imaging technology to prevent overload by monitoring temperature rises at various test points Depending on the temperature increase, actions can range from issuing warnings and enhancing cooling methods (either air or oil) to reducing the transformer load If these measures prove ineffective and the temperature continues to exceed permissible limits for an extended period, the transformer will be disconnected from the system to ensure safety.

The principles of relay protection are fundamental in ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and isolate affected sections, minimizing damage and maintaining system integrity Understanding the key concepts of relay protection, including selectivity, sensitivity, and speed, is essential for effective implementation Properly configured relay systems enhance operational efficiency and reduce the risk of catastrophic failures, making them a critical component in modern electrical engineering.

CALCULATION OF SHORT CIRCUIT

CALCULATION OF REACTANCE VALUE

Select S cb = 25 MVA, calculation in the relative system.

Basic voltage equal to average voltage at voltage level:

4.1.1 Calculation of reactance value of element in maximum power system mode

Subtation has two parallel transformers:

The same positive sequence schema but don’t have E:

The principles of relay protection are essential for ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and initiate timely disconnection of affected circuits, preventing damage to equipment and maintaining system stability By implementing effective relay protection strategies, operators can enhance the overall performance of power systems, reduce downtime, and ensure compliance with safety standards Understanding these principles is crucial for engineers and technicians involved in the design and maintenance of protective relaying systems.

4.1.2 Calculate the resistances in the minimum system capacity mode

Power of system: S HT = 1700 MVA Transformer station operates with 1 transformer.

Resistance of system: X ' 11 = X ' HT = S cb

The same positive sequence schema but don’t have E:

The principles of relay protection are essential in ensuring the safety and reliability of electrical systems These principles involve various protective methods designed to detect faults and initiate corrective actions to prevent damage Effective relay protection relies on accurate sensing, timely response, and coordination among protective devices Understanding these principles is crucial for engineers and technicians to maintain system integrity and enhance operational efficiency By implementing robust relay protection strategies, organizations can minimize downtime and ensure the longevity of their electrical infrastructure.

CACULATE SHORT-CIRCUIT CURRENT

The all short circuit point:

The resistance of the components along the line in the modes and diagrams is calculated using the formula X D23 = X D34 = X D45 = X D56 = 1/4 X D, where X D equals 0.039, resulting in a resistance of 0.0098 For the different types of short circuits that require calculation, refer to the formula provided in the accompanying table.

Type of short circuit X (n) Δ m (n) Calculate

The principles of relay protection are essential in ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and initiate corrective actions to prevent equipment damage Understanding the fundamental concepts of relay protection helps in implementing effective strategies for maintaining system integrity By utilizing various protective relays, operators can quickly identify issues and minimize downtime, ensuring continuous operation Proper application of these principles not only enhances system performance but also safeguards against potential hazards in electrical networks.

4.2.1 Calculate short-circuit current in maximum system power mode

Short-circuit types to consider:

N (1) – Line to ground short circuit

N (1,1) - Double phase short circuit with ground connection a) 2 transformers parallel

The total resistance positive, negative, zero when the short circuit at the point N1:

X N1∆ = X N12∑ + X N10∑ = 0,011+0,012 = 0,023 Current of phase A in positive:

I (1) N1 =m (1) I Na (1) 1 =3.29,41,23 Short circuit current in zero:

Current of phase A in positive:

The principles of relay protection are essential for ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and isolate them quickly, preventing damage to equipment and maintaining system stability By implementing effective relay protection strategies, utilities can enhance their operational efficiency and minimize downtime Understanding the core principles behind relay protection is crucial for engineers and technicians working in the field of electrical engineering.

(0,011+0,012) 2 59,88,85 Three-phase shortcircuit current in zero:

The total resistance positive, negative, zero when the short circuit at the point N2:

Current of phase A in positive:

Short circuit current in zero:

Current of phase A in positive:

The principles of relay protection in protective methods are essential for ensuring the safety and reliability of electrical systems These principles involve the use of protective relays to detect faults and initiate appropriate actions to isolate affected sections of the system By implementing effective relay protection strategies, utilities can minimize damage to equipment and maintain system stability Understanding the underlying principles of relay protection helps engineers design robust protective schemes that enhance overall operational efficiency and safety in power systems.

Three-phase shortcircuit current in zero:

The total resistance positive, negative, zero when the short circuit at the point N3

X N3∆ = X N 32∑ + X N 30∑ = 0,057 +0,075 = 0,132 Current of phase A in positive:

I (1) N3 =m ( 1) I (1) Na1 =3.5,29,87 Short circuit current in zero:

Current of phase A in positive:

Relay protection is a critical component in electrical engineering, ensuring the safety and reliability of power systems The principles of relay protection focus on detecting faults and isolating affected sections to prevent damage This method involves using various protective relays that monitor electrical parameters and respond to abnormalities By implementing effective relay protection strategies, systems can maintain operational integrity and minimize downtime Understanding these principles is essential for professionals in the field to enhance system resilience and ensure efficient fault management.

Three-phase shortcircuit current in zero:

At point N4, N5, N6 Similar calculation we have:

Table of short circuit of max mode with 2 transformer working in parallel

The same in 2 transformer mode works in parallel

The total resistance positive, negative, zero when the short circuit at the point N2 :

Relay protection is a critical aspect of electrical systems, ensuring safety and reliability It involves the use of protective relays to detect faults and initiate corrective actions The principles of relay protection include sensitivity, selectivity, and speed, which are essential for minimizing damage during electrical faults Effective relay protection systems must be designed to respond promptly while isolating only the affected sections of the network Understanding these principles is vital for engineers and technicians to maintain the integrity of electrical installations.

X N2∆ = X N22∑ + X N20∑ = 0,083+0,084 = 0,167 Current of phase A in positive:

=3.4 Short circuit current in zero:

Current of phase A in positive:

( 0,083+0,084 ) 2 8,02,02 Three-phase shortcircuit current in zero:

Table of short circuit of max mode with 1 transformer working

Relay protection is essential in electrical systems, ensuring safety and reliability It involves the use of protective relays to detect faults and initiate corrective actions The principles of relay protection include sensitivity, selectivity, and speed, which are crucial for minimizing damage during electrical faults Proper coordination among relays enhances system stability and prevents unnecessary outages Understanding these principles is vital for engineers and technicians to design effective protection schemes that safeguard equipment and maintain operational integrity.

4.2.2 Calculate short-circuit current in minimum system power mode

The type of short circuit:

N (1) – Line to ground short circuit

N (1,1) - Double phase short circuit with ground connection a) 2 transformers working parallel

The total resistance positive, negative, zero when the short circuit at the point N1

XN’1∆= XN’12∑ + XN’10 = 0,015+0,017 = 0,032 Short-circuit current at N1:

Short cirtcuit current in zero:

Current of phase A in positive:

Relay protection is essential for ensuring the safety and reliability of electrical systems It involves the use of protective relays to detect faults and initiate necessary actions to isolate affected components Understanding the principles of relay protection is crucial for effective system operation and maintenance Key concepts include the types of relays, their operational characteristics, and the coordination of protective devices to minimize system disruptions Proper application of these principles enhances system resilience and prevents damage from electrical faults.

( 0,015 +0,017 ) 2 43,54e,35 Three-phase shortcircuit current in zero:

Table of short circuit of min mode with 2 transformer working in parallel

The same in 2 transformer mode works in parallel

The total resistance positive, negative, zero when the short circuit at the point N2 :

Relay protection is a crucial aspect of electrical systems, designed to detect faults and ensure the safety and reliability of power networks Understanding the principles of relay protection involves recognizing how relays monitor electrical parameters and respond to abnormal conditions Effective protective methods rely on accurate sensing, timely response, and coordination among various protective devices By implementing robust relay protection strategies, systems can minimize damage during faults, enhance operational efficiency, and maintain the integrity of electrical infrastructure.

- Short circuit N(1): XN’2∆= XN’22∑ + XN’20∑ = 0,087+0,089 = 0,176

0,087 + 0,176 ,41 Short circuit current in zero:

0,087+0,089 =0,044 Current of phase A in positive:

Three-phase shortcircuit current in zero:

Table of short circuit of min mode with 1 transformer working

The principles of relay protection are essential in ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and isolate affected sections, preventing damage to equipment and maintaining system stability By implementing effective relay protection strategies, operators can enhance the overall performance of electrical networks and minimize the risk of outages Understanding these principles is crucial for engineers and technicians involved in power system management and maintenance.

Relay protection is essential in safeguarding electrical systems, ensuring reliable operation and minimizing damage during faults The principles of relay protection involve detecting abnormal conditions and initiating appropriate responses to isolate affected components By employing various protective methods, including overcurrent, differential, and distance protection, systems can effectively mitigate risks Understanding these principles is crucial for engineers and technicians to design robust protection schemes that enhance system resilience and operational safety.

CALCULATE PROTECTION FOR LINE

SHORT-CIRCUIT CURRENT IN SOME CASES ON LINE L

When two transformers operate in parallel, their combined resistance is halved compared to when a single transformer functions independently Consequently, the maximum short-circuit current on the line during a fault will occur under maximum system power conditions with both transformers in parallel Conversely, the minimum short-circuit current will be observed when only one transformer operates independently during a short-circuit event.

Table 6.1 Short-circuit currents in max system power mode, 2 transformers:

Table 6.2 Short-circuit currents in min system power mode, 1 transformer:

We calculte instantaneous overcurrent relay, maximum overcurrent relay, zero overcurrent relay prrotection for line L.

1 The threshold current of protection

The threshold current : with: k at – safety factor, k at = 1,2

The maximum external short-circuit current, denoted as I Nngmax, is a critical parameter that represents the largest short-circuit current that can occur in a system Typically, this value is equivalent to the short-circuit current at the end of a line, which is a crucial consideration in electrical design and safety assessments.

Relay protection is a critical component in electrical systems, ensuring safety and reliability by detecting faults and isolating affected areas Understanding the principles of relay protection involves recognizing its role in monitoring electrical parameters, responding to anomalies, and preventing equipment damage Effective protective methods rely on accurate settings and coordination among relays to minimize disruption during faults By implementing advanced technologies and adhering to industry standards, relay protection systems enhance the overall stability of power networks.

- The external short-circuit current of line L:

The maximum external short-circuit current: 9,01

The minimum external short-circuit current: 7,39

- The threshold current for instantaneous overcurrent relay protection of line L :

Protect area of instantaneous overcurrent relay

The protected area is defined as the distance along the protected line, measured from the protection point to the location where the short-circuit current matches the threshold current of the protection system.

- The largest protection area: (Lmax)

Max shortcircuit currentMin shortcircuit currentThreshold current

The principles of relay protection are fundamental in ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and initiate corrective actions to prevent damage to equipment and maintain system stability Effective relay protection involves understanding various protection schemes, settings, and coordination among devices to ensure prompt and accurate responses to abnormal conditions Implementing these principles not only enhances the operational efficiency of electrical networks but also safeguards personnel and infrastructure from potential hazards Properly designed relay protection systems are essential for the longevity and performance of electrical installations.

MAXIMUM OVERCURRENT RELAY

The threshold current : with: kat –Safety factor, kat = 1,2 kmm – Open factor, kmm = 2 kv - Return coefficient selected for digital relay: kv = 0,95

Ilvmax- The largest working current, Ictlvmax = 238,57 A

Convert maximum working current to relative unit system:

I 13,5 ¿ −1 xTMS with with : TMS: constant time set of relay (s).

I ¿ : Short-circuit current through relay.

Relay protection is a critical component in electrical systems, ensuring the safety and reliability of power distribution The principles of relay protection involve detecting faults and initiating corrective actions to prevent damage to equipment These protective methods utilize various types of relays that monitor electrical parameters and respond to abnormal conditions Understanding these principles is essential for designing effective protection schemes that maintain system integrity and minimize downtime Proper implementation of relay protection not only enhances operational efficiency but also safeguards personnel and infrastructure from potential hazards.

- Short circuit point N6: IN6 max = 9,01

Impact time characteristics at N6 t = I 13,5 ¿ −1 xTMS

- Short circuit point N5: IN5 max = 9,88

 t 5 = 10,29−1 13,5 x 0,62 = 0,9(s) Similar calculations for short circuits on the line we have

Table 6.3 Impact time of the max system

Table 6.4 Impact time of the min system

The principles of relay protection are essential for ensuring the safety and reliability of electrical systems These protective methods are designed to detect faults and initiate timely disconnection of affected circuits, preventing damage to equipment and ensuring operational continuity Understanding the various types of relay protection, including overcurrent, differential, and distance relays, is crucial for effective system management Implementing these principles not only enhances system resilience but also complies with industry standards and regulations, ultimately safeguarding both personnel and infrastructure.

CALCULATE ZERO PROTECTION (TTK)

-Threshold current of protection with: k 0 - adjustment coefficient, k = 0,3

I dmBI - Rated current of the current transformer set for the line.

The working time of overcurrent protection does not have time to select according to independent characteristics:

Time characteristics impact of overcurrent protection TTK

CHARACTERISTICS OF THE TIME OF OVERCURRENT PROTECTION t max mode t min mode

The principles of relay protection are essential in ensuring the reliability and safety of electrical systems Effective relay protection methods are designed to detect faults and isolate affected areas promptly, minimizing damage and maintaining system stability Understanding the underlying principles of these protective methods allows for the optimization of protection schemes, enhancing the overall efficiency of power distribution networks Implementing robust relay protection strategies is crucial for safeguarding equipment and ensuring uninterrupted service in electrical installations.

CHECK THE WORK OF PROTECTION FOR

CHECK THE WORK OF THE TRANSFORMER PROTECTION

7.1.1 Check the work of the transformer protections compare offset current with braking a Checking safety factor in the brake when short circuit in external over current.

To checksafety factor in the brake when short circuit in external over current, we check when short circuit in enternal over current is the largest.

The maximum short circuit current at N2 is crucial for protection in every MBA, where the highest short circuit current is N (3) within the maximum power system This scenario assumes that one transformer operates independently.

=¿ 12,05 The largest short circuit current go through protection in every transformer is N (1,1) in the max power system, 1 transformer work independently

I (1,1) N2 BVmax =I (1.1) N 2 ,02 Conclusion, short circuit in external protection by:

I SL =I kcbtt max =f imax K dn K kck I N ngmax ¿ 0,1.1 1,8.12,05=2,17

I H =2 I N ngmax =2.12,05$,1 Safety factor in the brake is defined by fomula:

With I Htt is calculate restrain current Straight line I SL = 1,34 cut characteristic (c) so:

To ensure the effectiveness of brake protection systems, it is crucial that they remain unaffected by short circuits occurring outside the designated protection zone However, when a short circuit happens within the protection zone, the difference in supply current (I SL) consistently matches the damping current (I H), which guarantees the reliable operation of theoretical relays To verify the performance of these relays, it is essential to assess their sensitivity.

Relay protection is a critical aspect of electrical systems, ensuring the safety and reliability of power distribution The principles of relay protection involve detecting faults and initiating appropriate responses to isolate affected areas, thereby preventing damage to equipment and maintaining system stability Effective protective methods include the use of various relay types, each designed for specific applications and fault conditions Understanding the fundamental principles of relay protection is essential for engineers and technicians to implement robust protection schemes that enhance system performance and minimize downtime.

With: I kd – starting current in protection

To check the sensitivity of the protection, we consider the smallest short-circuit current when a short circuit occurs in the protection zone (at N1’ and N2’)

Following to calculate in chapter 4, The smallest short-circuit current that passes through short circuit protection at N1 'is a two-phase short-circuit when the system power is minimum

Straight line I H = 57,74 cut characteristic line (d)

 So, protection ensure to cut safely when having short circuit at N1’

In Chapter 4, we calculate the smallest short-circuit current at N2 during a two-phase short-circuit, which occurs under minimum system power conditions with two transformers operating in parallel.

Straight line I H = 16,98 cut starting characteristic current line at characteristic segment (c)

So, protection ensure to cut safely when having short circuit at N2’

Relay protection is essential for ensuring the safety and reliability of electrical systems It involves various protective methods designed to detect faults and isolate affected sections of the network Key principles of relay protection include selectivity, sensitivity, and speed of operation, which help minimize damage and maintain system stability Understanding these principles is crucial for engineers and technicians to design effective protection schemes that enhance the overall performance of electrical installations By implementing advanced relay protection strategies, the risk of equipment failure and power outages can be significantly reduced, ensuring a more resilient power supply.

The impact characteristics of the braking differential protection applied to the MBA

7.1.2 Check the work of over fast cutting current

Sensivity of protection is defined by formula: k N = I N min

I kd with condition Sensivity of protection : k N = I Nmin

 So protection get requirement for sensitive level.

7.1.3 Zero sequence in earth fault ( TTK)

Sensivity of protection is defined by formula: k N = I N min

I kd with condition Sensivity of protection :

The principles of relay protection are fundamental in ensuring the safety and reliability of electrical systems Relay protection methods are designed to detect faults and isolate affected sections of the network, thereby preventing damage and maintaining operational integrity Understanding the key concepts of relay protection, such as current and voltage settings, is essential for effective implementation By applying these principles, engineers can enhance system resilience and minimize downtime, ultimately leading to improved performance and safety in electrical networks.

 So protection get requirement for sensitive level.

CHECK THE WORK OF THE PROTECTIONS IN THE LINE

 Check sensivity of protection. k N = I Nmin

 So protection get requirement for sensitive level.

The smallest short circuit currenr TTK go through protecting is short circuit

N (1,1) current at N6 in the minimum power system.

=> So protection get requirement for sensitive level.

Sensivity of protection is defined by formula: k N = I N min

I kd with condition Sensivity of protection : k N = I Nmin

=> So protection get requirement for sensitive level.

7.2.3 Zero sequence in earth fault (TTK)

Sensivity of protection is defined by formula: k N = I N min

Relay protection is essential for ensuring the safety and reliability of electrical systems It involves the use of protective relays to detect faults and initiate corrective actions, thereby preventing damage to equipment and maintaining system stability Understanding the principles of relay protection is crucial for effective system design and operation Key concepts include the types of relays, their operating principles, and the coordination of protection schemes to ensure rapid fault isolation Implementing these principles enhances system resilience and minimizes downtime, making relay protection a fundamental aspect of modern electrical engineering practices.