1). What is a Marshalling Panel?
A marshalling panel is used for collecting, organizing and interfacing control cables between field devices and control panels.
It is commonly used in:
- Substations,
- Power plants,
- DCS systems and
- PLC systems.
Functions include:
- Terminal interfacing and
- Signal segregation.
2). Which software used for electrical drafting?
Commonly used software includes:
- AutoCAD,
- AutoCAD Electrical,
- EPLAN,
- Revit MEP,
- MicroStation and
- SolidWorks Electrical.
3). What is a Single Line Diagram (SLD)?
A Single Line Diagram is a simplified representation of an electrical system using single lines and symbols to show:
- Transformers,
- Circuit breakers,
- Busbars,
- Feeders,
- Loads and
- Protection devices.
It helps engineers understand power flow and system configuration.
4). What is the difference between schematic and wiring diagrams?
| Schematic Diagram | Wiring Diagram |
|---|---|
| Shows functional operation | Shows actual physical wiring |
| Used for understanding circuits | Used for installation |
| Symbol-based | Connection-based |
5). What are electrical symbols?
Electrical symbols are standardized graphical representations of electrical components such as:
- Switches,
- Circuit breakers,
- Motors,
- Transformers,
- Relays,
- Lamps and
- Earthing points.
These symbols are utilized in electrical drawings for easy understanding.
6). What is the importance of layer management in AutoCAD?
Layer management helps to organize drawings efficiently by separating:
- Power cables,
- Lighting circuits,
- Earthing systems,
- Dimensions and
- Text annotations.
Advantages include:
- Easy editing,
- Better visibility,
- Faster troubleshooting and
- Improved printing quality.
7). What is an as-built drawing?
An as-built drawing is the final updated drawing showing the actual installed condition after project completion including any site modifications.
8). Explain cable tray layout drawing.
Cable tray layout drawings show:
- Cable tray routing,
- Tray sizes,
- Elevation levels,
- Supports,
- Bends and tees,
- Equipment connections.
These drawings help in proper cable management.
9). What is a panel GA drawing?
GA (General Arrangement) drawing shows the physical arrangement of electrical panels including:
- Dimensions,
- Component locations,
- Front and side views,
- Cable entry points,
- Busbar arrangements.
10). What is the purpose of earthing drawings?
Earthing drawings show:
- Earth pit locations,
- Earthing conductor routing,
- Equipment earthing connections and
- Earth grid layouts.
They ensure personnel and equipment safety.
11). What are the common types of electrical drawings?
Common electrical drawings include:
- Single Line Diagram (SLD),
- Wiring Diagram,
- Control Schematic,
- Cable Schedule,
- Lighting Layout,
- Power Layout,
- Earthing Layout,
- Panel Layout and
- Cable Tray Layout.
12). What is a cable schedule?
A cable schedule is a document containing:
- Cable number,
- Cable size,
- From and to locations,
- Cable type,
- Core details and
- Route information.
It helps during installation and maintenance.
13). What is the difference between power layout and lighting layout?
| Power Layout | Lighting Layout |
|---|---|
| Shows sockets and power outlets | Shows light fittings |
| Used for equipment supply | Used for illumination |
| Higher load circuits | Lower load circuits |
14). What is the standard scale used in electrical drawings?
Common scales include:
- 1:50
- 1:100
- 1:200
Scale selection depends on project size and detail requirements.
15). What are title blocks in drawings?
Title blocks contain project information such as:
- Project name,
- Drawing title,
- Drawing number,
- Revision number,
- Date,
- Prepared by and
- Approved by.
16). What is revision control in drafting?
Revision control tracks modifications made to drawings using revision numbers and descriptions to avoid confusion during project execution.
17). What is the importance of electrical drafting standards?
Standards ensure:
- Uniformity,
- Accuracy,
- Safety compliance and
- Easy understanding among engineers and technicians.
Common standards:
- IEC
- IEEE
- IS Standards
- NEC
18). What is a busbar in electrical systems?
A busbar is a metallic conductor used for distributing electrical power within switchboards and substations.
19). What are the common mistakes to avoid in electrical drafting?
Common mistakes include:
- Wrong dimensions,
- Missing labels,
- Incorrect symbols,
- Layer confusion,
- Improper scaling and
- Cable routing clashes.
20). How to ensure drawing accuracy?
Accuracy is ensured by:
- Cross-checking calculations,
- Reviewing standards,
- Coordinating with engineers,
- Using proper layers and templates and
- Verifying dimensions and symbols.
21). What is voltage drop? Why is it important?
Voltage drop is the reduction in voltage across a cable due to resistance. Excessive voltage drop can cause:
- Equipment malfunction,
- Overheating and
- Reduced efficiency.
22). What is the difference between LT and HT drawings?
| LT Drawings | HT Drawings |
|---|---|
| Low voltage systems | High voltage systems |
| Up to 1 kV | Above 1 kV |
| Building electrical layouts | Substation and transmission systems |
23). What is interlocking in electrical panels?
Interlocking prevents unsafe operations by ensuring equipment operates in a specific sequence.
Example:
- Preventing two breakers from closing simultaneously.
24). Explain the importance of cable derating.
Cable derating reduces cable current carrying capacity due to factors such as:
- High ambient temperature,
- Grouped cables,
- Underground installation and
- Poor ventilation.
Improper derating may cause:
- Overheating,
- Insulation damage and
- Fire hazards.
25). What is the difference between AutoCAD and AutoCAD Electrical?
| AutoCAD | AutoCAD Electrical |
|---|---|
| General drafting software | Specialized electrical drafting |
| Manual symbol insertion | Built-in electrical libraries |
| Limited automation | Automatic wire numbering and reports |