|September 26 | Tata Steel | Wipro | HDFC AMC | Fortis Healthcare | BASM

 Tata Steel: Global credit rating agency Moody’s has upgraded the corporate family rating of Tata Steel from Ba1 to Baa3, and changed the outlook from Positive to Stable. The rating agency expects the company's profitability to increase even as softer steel prices dent revenues, and the company to maintain conservative financial policies with a well-balanced capital allocation and financial metrics appropriate for its Baa3 rating.

Wipro: The IT services company announced the sale of land measuring 14 acres and 02 cents, in Chennai, together with a 20-year-old building for Rs 266.38 crore. The company executed the sale deed on September 25 and Casagrand Bizpark was the buyer.

Fortis Healthcare: The company has received approval from the board of directors to enter into a Share Purchase Agreement for acquiring a 99.9% stake in Artistry Properties. The enterprise value of the stake buy is Rs 32 crore. Artistry owns a land and building adjacent to Fortis Hospital at Anandpur in Kolkata. The building is entirely constructed with all statutory compliances in place and with minimal customization and re-layout, it can be utilized for accommodating OPD, diagnostics, and daycare services, relocated/shifted from the main building of Fortis Anandpur Hospital.

HDFC Asset Management Company: HDFC AMC has invested Rs 25 crore in its subsidiary HDFC AMC International (IFSC) and continues to hold a 100% stake in the subsidiary.

Bannari Amman Spinning Mills: Shareholders have given approval for the reappointment of S V Arumugam as Managing Director of Bannari Amman Spinning Mills, for three years with effect from June 27, 2023, to June 26, 2026. They also approved an appointment of C Sivasamy as an Independent Director of the Company for 5 consecutive years, from June 28, 2023 to June 27, 2028.

Electrical Engineers: Basic Interview Questions

 What are the primary responsibilities of an electrical engineer?

The primary responsibilities of an electrical engineer are to create, design, test, and observe the electrical components of a project. This is a vast field, and projects within this field can vary from manufacturing products to designing power grids. Due to its vast field, the responsibilities can vary from position to position.

The key responsibilities of an electrical engineer are as follows:

• Fixing and troubleshooting of devices.
• Conducting the functionality tests.
• Analyzing current trends and information.
• Developing manufacturing processes for building and assembling electrical components etc.

What are the critical skills required to become an electrical engineer?

The main task of an electrical engineer is to take care of the components of the electrical system. To prevent and troubleshoot such failures, a skilled electrical engineer must do the following things:

• Analyze data to get top trends.
• Communicate clearly with supervisors and clients to get the decision efficiently.
• Keep up to date on emerging trends within the industry.
• Adhere to strict safety codes.
• Work in tandem with supervisors and management.

What are the fundamental components of electrical circuits?

Following are the fundamental components of electrical circuits:

• Active Circuits: Active Circuits are the elements used to generate energy from within their system as a form of source.
• Passive Circuits: Passive circuits are the elements that allow the electric current to pass through it and do not generate any energy from it.
• AC or DC Circuits: AC stands for Alternating Current, and DC stands for Direct Current. AC always produces some fluctuating current, whereas DC always produces a stable current in a constant source.
• Series Circuits: When the electrical components are connected in series within a circuit, it is known as a series circuit.
• Parallel Circuits: When the electrical components are connected in parallel within a circuit, it is known as a parallel circuit.

What is the definition of an ideal transformer?

A transformer is called an ideal transformer if there no losses happen at all. In other words, we can say that, in an ideal transformer, the transformer input authority should be equivalent to the output authority of the transformer, i.e., they have 100% competence.

What are the different types of networks used to build an electrical circuit?

There are mainly two types of networks used to build an electrical circuit called Passive or Active Networks. A Passive network is a network that contains passive elements in its network, such as Resistance, Capacitance, or Inductance. On the other hand, an Active Network is a network that contains active elements in its network, such as Current or Voltage Sources.

What are some essential tools used for the measurement of electrical parameters in an electrical circuit?

Following is the list of some measuring tools used for the measurement of electrical parameters:

• Voltmeter
• Ammeter
• Ohmmeter
• Multi-meter
• Power meter
• Microwave meter
• Cathode Ray Oscilloscope
• Signal Generators and Analyzers
• Wattmeter
• Sweep Generator etc.

Gas Insulated Substations (GIS)

 

High Voltage Gas Insulated Substations (GIS) are one-time installations having a very long operating life with minimal maintenance, unlike Air Insulated Substations (AIS). However, being a complex and high-cost construction, the operation and maintenance of GIS is still an elusive topic that requires a closely coordinated plan and schedule based on the manuals and instructions of OEMs.

They draw a lot of similarities, as well as quite a few differences from their conventional counterpart, AIS.

After its inception in the mid-1960s, GIS technology has become a remarkable success over a wide range of high voltage applications up to 800 kV. Reliable operation and compact size have been its main advantages over its conventional air-insulated counterparts. Despite a very high initial capital cost, these two advantages reflect in other multiple aspects like low maintenance, minimum footprint, enhanced safety, pleasing aesthetics, and so on.

Operating a GIS module could be a challenge for untrained operators because of completely encapsulated switchgear, measuring equipment, and conducting parts. Although the components and operations are principally similar to an AIS, the physical arrangement of those elements marks a notable difference.

The presence of metallic enclosure and unavailability of visible indication of component operations require getting used to. Furthermore, a GIS module requires stringent interlocking schemes between breakers, maintenance switches, and earthing switches to ensure safe operation and maintenance.

WORKING PRINCIPLE OF VFD

It is important to be familiar with the working principle of VFDs as they are extensively used in AC motor-driven applications. VFD has greater functionality and operation capabilities than conventional motor drives, which will be explained in detail in this article.

Let’s take a 3-phase load as an example to see how VFDs work. Firstly, when AC power is supplied from the mains, it directly passes through the first VFD stage – Rectifier stage. The current passes through six diodes that convert the AC-supplied current into DC. In short, each of the three phases is connected to one pair of diodes, which only allow the peak of each phase to pass through it.

Therefore, the output of the 3 phases passing through diodes, when measured by an oscilloscope.

the output current looks like a rough DC or just a current wave that doesn’t include the negative side of the current. Therefore, this current needs to be converted into a healthy DC and the best way to achieve that is by connecting a capacitor that will smooth the output current.

This capacitor is the VFD’s second stage, called the DC filter. Because of the charging and discharging effect of the capacitor, the current passing through the DC filter will have a wave.

After the DC is considered smooth, it is ready to pass through the third stage of the VFD – the IGBTs inverter to convert it into AC again. When the current reaches this stage, the converted AC’s frequency could be varied accordingly. The connected number of IGBTs here will be turned on and off very fast to produce an AC-like waveform that will run the connected motor as if it was connected directly to an AC supply.

The IGBTs here act like switches that when rapidly switched on and off, create the Pulse-Width Modulation (PWM) that is a key to allowing a VFD to control the speed of the motor.

Variable Frequency Drive (VFD)

 

For many years, the major challenge to some motor-driven applications was the inability to control their speed. However, the advent of reliable power electronics made it possible to control the speed of motors using variable-frequency drivers.

VFDs are widely used in many applications nowadays. The main reason is that they have greater functionality and operation capabilities compared to conventional motor drives when starting a motor.

The working of VFD is based on the control of frequency and voltage simultaneously through a PWM inverter, it is used to control the speed of AC motor-driven applications. In addition, variable frequency drives offer protections like phase, under, and overvoltage protection.

Components of VFD

To understand the working principle of a variable frequency driver, it is important to know what it is composed of. In other words, you need to know what leads the currents passing through a VFD of a 3-phase motor, for instance, to be changed from AC to DC and then back to AC again.

VFD comprises three main sections: Rectifier, Filters, and Inverter.

1. Rectifier: The first stage of VFD. It converts AC power fed from the mains to DC power. It mainly utilizes diodes that are connected in parallel to convert AC power into DC.
2. Filter: A capacitor that is used to smooth the rectified DC power.
3. Inverter: Transistors (IGBTs) used to work to be switched on and off rapidly to create a pulse-width modulation which creates an AC-like wave that will allow the VFD to control the speed of the motor.

"Why Do You Want To Work Here?"

 

"Why Do You Want To Work Here?"

The hiring manager is trying to get at your underlying motivations for wanting this job. Are you here just for a paycheck, or do you see yourself becoming an integral part of the company and growing along with it?

You need to show them that you want to become “part of the family.” At the same time, however, show how your “wants” coincide with their “needs.”

EXAMPLE ANSWER:

“One thing that really attracted me to your company and this opportunity is the company’s dedication to its local community. I’m a community-oriented person, both on and off the job. Along with preferring a work environment with an exceptional culture – such as the one your company offers – I value employers that look outside their walls for opportunities to make a difference. I feel your company does that to a degree you don’t typically see, and I want to be a part of a business like that.”

"What Is Your Greatest Strength?"

"What Is Your Greatest Strength?"

This is a fairly straightforward question to handle. Talk about a “strength” that you know the company puts a lot of value in.

EXAMPLE ANSWER:

“My biggest strength is my problem-solving capabilities. Generally, I’m a methodical person with exceptional research skills. However, I’m also comfortable thinking outside of the box. When taken together, that allows me to navigate the unknown with greater ease. I know how to track down the information I need, as well as how to look deeper, creating opportunities to innovate when I need solutions.”

"Why Should We Hire You?"

 

"Why Should We Hire You?"

This is another incredibly common question, and it gives you a great opportunity to stand out from the crowd and really show the hiring manager how you can help the company.

The key thing to remember here is: be specific.

Leverage your company research and the job description to find exactly why the company is hiring someone for this position. What problem/pain point does the new hire have to solve? You need to show that you are the perfect candidate that can solve those problems/pain points.

EXAMPLE ANSWER:

“After reviewing your job description, it was clear that finding someone with a willingness to learn that would face challenges head-on was a priority. Generally, I relish opportunities to explore the unknown, and I’m eager to glean all I can from those around me. Additionally, I understand the value of doing my own research to find answers, as well as asking intelligent questions of those around me. Taken together, I think that makes me an exceptional fit in that regard, making me an excellent candidate for the role.”

"Tell Me About Yourself..."

 

"Tell Me About Yourself..."

This classic opening question should probably be put out to pasture, but it’s still one of THE most common interview questions you’ll face. With that being said, it still seems to trip up a ton of job seekers every year.

EXAMPLE ANSWER:

“For the past five years, I’ve been working in a fast-paced nursing role in one of the area’s top hospitals. During that time, I’ve not only had the opportunity to learn from some of the leading specialists in their field, but I’ve also furthered my education.

“I’ve recently graduated with a nursing degree and have completed my initial licensing requirements. At this time, I am eager to take the next step in my career, allowing me to put my knowledge and experience to work in a challenging role.”

Electrical Testing Engineer Interview Questions and Answers

What are the most important skills of an electrical test engineer to have?

This question can help the interviewer determine if you have the skills and qualifications to succeed in this role. Use your answer to highlight your technical, communication and problem-solving skills.

Example: “The most important skill for an electrical test engineer is their ability to communicate effectively with others. Electrical engineers need to be able to clearly explain their ideas and concepts to other members of a team. I also think it’s important to have strong technical skills because they allow me to understand complex problems and develop solutions. Finally, I believe that being organized and detail-oriented are essential skills for electrical test engineers.”

Provide an example of a time when you had to work with a difficult or challenging customer.

Interviewers may ask this question to assess your customer service skills. They want to know how you handle conflict and whether or not you can resolve it in a professional manner. In your answer, try to focus on the steps you took to solve the problem and maintain a positive relationship with the customer.

Example: “In my previous role as an electrical test engineer, I had a difficult customer who would often call me at all hours of the day about issues they were having with our software. This made it challenging for me to get any work done because I was constantly answering their questions. Eventually, I scheduled a meeting with them to discuss the issue. We talked through some of the challenges they were having and came up with a solution that allowed them to use the software more effectively.”

If hired, what would be your priorities during your first few weeks on the job?

This question helps the interviewer determine how you plan to fit into their team and what your goals are for your first few weeks on the job. Your answer should include a list of things you would do to get acclimated to your new role, including meeting with coworkers and learning about company policies and procedures.

Example: “During my first week, I would want to meet as many people in the office as possible. I also plan to spend time getting familiar with the company’s computer systems and any other resources that will help me complete my work. I would also like to learn more about the projects we’re currently working on so I can contribute to them from day one.”

What makes you the best candidate for this electrical test engineer position?

This question is your opportunity to show the interviewer that you are qualified for this role. Use examples from your experience and education to highlight your skills, knowledge and abilities.

Example: “I have a bachelor’s degree in electrical engineering technology with an emphasis on software development. I also have five years of experience as an electrical test engineer at my current company where I’ve worked on projects like developing new products and testing them for safety. My background in both hardware and software development makes me well-suited for this position.”

Which electrical components or systems have you tested in the past?

This question can help the interviewer understand your experience level and how you apply it to a new role. Use examples from your resume or past projects to highlight your skills and abilities as an electrical test engineer.

Example: “In my last position, I tested all of the components in a power grid system that was used for a large-scale solar farm. The project required me to work with several other engineers to ensure we were testing each component correctly and efficiently. We also had to make sure our tests didn’t interfere with the operation of the entire solar farm. My knowledge of the different systems helped us complete the project on time.”

What do you think is the most challenging part of being an electrical test engineer?

This question can help interviewers understand what you think about your job and how it relates to the company. They may want to know that you enjoy working as an electrical test engineer, but they also might appreciate hearing about any challenges you’ve faced in this role. Consider discussing a challenge you have experienced and how you overcame it or plan to overcome it.

Example: “The most challenging part of being an electrical test engineer is finding ways to improve testing processes. I love my work because I get to solve problems every day, but sometimes it’s hard to find new solutions when we’re doing something over and over again. However, I try to look at each project with fresh eyes and consider different approaches.”

How often do you update your knowledge and skills as an electrical test engineer?

This question can help interviewers understand how you approach your career and whether you’re open to learning new things. Your answer should show that you are committed to continuous improvement, but it’s also important to mention specific ways you’ve done this in the past.

Example: “I am always looking for ways to improve my skills as an electrical test engineer. I have taken several online courses on topics like digital testing and automated testing. These courses helped me learn more about these processes and apply them to my work. In addition, I regularly read industry publications and attend conferences to stay up-to-date with current trends.”

Compensating CT Ratio Mismatch | Differential Protection

 Compensating CT ratio mismatch is a very important step in configuring a differential protection. This may be achieved by specifically selecting the CT ratios or in modern relaying, configured through the relay software.

The concept of zero sequence currents was discussed including how they affect the performance of transformer differential protection and how to compensate for them. Zero sequence compensation is a form of phase compensation. While zero sequence compensation is very important in differential protection, compensating CT ratio mismatch through magnitude compensation or commonly known as tap compensation is equally important.

When applying any kind of protection scheme, power system parameters are measured using instrument transformers. Current transformers (CTs) are used in transformer differential protection. These CTs are selected based on the amount of current they are expected to measure up to certain value of current, during fault conditions, in which they can measure without loss of accuracy. In their application to transformer differential protection, CTs are usually selected based on the full load rating of circuit. Therefore, it is normal that CTs on both sides of the power transformer have different CT ratio. By having different CT ratio, measured values in the relay will not be equal and will yield an IOP not equal to zero.

Compensating CT ratio mismatch using TAP compensation is based on the concept of selecting CT ratio based on the power transformer turns ratio. Let IP and IS be the transformer primary current values at the transformer high and low side, respectively, I1 and I2 be the secondary currents measured by the relay, CTR1 and CTR2 the current transformer ratio, and N1 and N2, the transformer winding turns. To make I1 equal to I2 in all normal conditions, the ratio of CTR1 to CTR2 should be equal to the transformer turns ratio N2/N1. For delta connected CTs at the secondary side, CT2, since

In most cases, selecting standard CTRs based on the required conditions is very difficult if not impossible without making any compromise.

Compensating CT ratio mismatch for transformer differential protection using numerical relays is quite straightforward. Relay measured currents are expressed to their primary values by multiplying CTR1 and CTR2 to I1 and I2, respectively. The primary values are then expressed to their per unit values based on the power transformer MVA and kV ratings. This process allows the current values used in the calculation of IOP to be equal in magnitude during normal conditions.

To consider the CT connection in tap compensation, a constant is included in the tap equation as shown below,

Compensating CT ratio mismatch works with phase compensation to ensure the reliability of transformer differential protection.

Figure 2. Tap and Phase Compensation

While setting the relay is a straightforward process, it should be kept in mind that understanding the basic concepts are very vital in the practice of power system protection.

Vector Group of Transformer

The naming convention popularly known as Vector Group of Transformer was established by the International Electrotechnical Commission (IEC) through IEC 60076-1. This was done in order to create a notation for three-phase transformer winding configuration.

Vector Group of Transformer: Common Symbol Designation

Y or y – star winding

D or d – delta winding

N or n – neutral

0 to 12 – phase displacement in terms of clock position in multiples of 30°

Distance Relay Characteristics

Some numerical relays measure the absolute fault impedance and then determine whether operation is required according to impedance boundaries defined on the R/X diagram.

Traditional distance relays and numerical relays that emulate the impedance elements of traditional relays do not measure absolute impedance. They compare the measured fault voltage with a replica voltage derived from the fault current and the zone impedance setting to determine whether the fault is within zone or out-of-zone. Distance relay impedance comparators or algorithms which emulate traditional comparators are classified according to their polar characteristics, the number of signal inputs they have, and the method by which signal comparisons are made.

The common types compare either the relative amplitude or phase of two input quantities to obtain operating characteristics that are either straight lines or circles when plotted on an R/X diagram. At each stage of distance relay design evolution, the development of impedance operating characteristic shapes and sophistication has been governed by the technology available and the acceptable cost.

Since many traditional relays are still in service and since some numerical relays emulate the techniques of the traditional relays, a brief review of impedance comparators is justified.

Principle of Distance Relay

Since the impedance of a transmission line is proportional to its length, for distance measurement it is appropriate to use a relay capable of measuring the impedance of a line up to a predetermined point (the reach point).

Such a relay is described as a distance relay and is designed to operate only for faults occurring between the relay location and the selected reach point, thus giving discrimination for faults that may occur in different line sections.

The basic principle of distance protection involves the division of the voltage at the relaying point by the measured current. The apparent impedance so calculated is compared with the reach point impedance. If the measured impedance is less than the reach point impedance, it is assumed that a fault exists on the line between the relay and the reach point.

The reach point of a relay is the point along the line impedance locus that is intersected by the boundary characteristic of the relay.

Since this is dependent on the ratio of voltage and current and the phase angle between them, it may be plotted on an R/X diagram. The loci of power system impedances as seen by the relay during faults, power swings and load variations may be plotted on the same diagram and in this manner the performance of the relay in the presence of system faults and disturbances may be studied.

Distance Protection

Distance relays are one of the most important protection elements in a transmission line.

Distance relays characteristics may be Mho, Quadrilateral, Offset Mho, etc. In the case of the  quadrilateral characteristic or long reaching mho characteristics, additional care may be  required to remain secure during heavy load.

These  relays may sometimes be set based in percentages of the line impedances, for example a  typical setting for zone 1 is 80% of the impedance of the line in order to not reach the remote  end, the zone 2 can be set at 120% of the impedance of the line in order to dependably  overreach the line, Zone 3 sometimes are disabled or set to cover an adjacent line.

In the case of parallel lines, the mutual coupling of these lines can cause distance relays to  under reach and over reach. For this reason the relay setting must consider this effect, some  relays have algorithms to compensate, but it is necessary to use the current of the parallel line  which adds complexity to the installation.

In some countries there criteria that a distance protection can not reach fault in other voltage  levels, because fault clearing times in sub transmission levels may be slower than fault clearing  times at the transmission level.

The problem of combining fast fault clearance with selective tripping of plant is a key aim for the protection of power systems.

To meet these requirements, high-speed protection systems for transmission and primary distribution circuits that are suitable for use with the automatic recloser of circuit breakers are under continuous development and are very widely applied.