unable to install grub in /dev/sda

[SHOBHA J]

when trying to install grub using a usb,a failure occurs(ubuntu 18.04)
the error is:
executing 'grub-install/dev/sda' failed
this is a fatal error

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CasperVersion: 1.394
Date: Mon Jun 18 10:11:05 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Phillip Susi (psusi)]

Your EFI system partition is corrupt; you will need to repair it with either dosfsck or Windows' chkdsk/scandisk.

[Samet Cömert (euphoric)]

The solution was manually partitioning the disk and choosing the installation location of grub to an efi partition. I guess ubuntu was trying to install the grub to a wrong partition, such as /dev/sda.